Yu Lexing was assigned to work in the General Political Department of the National Revolutionary Army and studied in Huangpu Military Academy. In Huangpu, he met Shen Jinghui (Shen Zui's sister), a school doctor who graduated from Hunan Xiangya Medical College. They fell in love freely and got married. On the eve of the Northern Expedition, Yu Lexing and his wife were transferred to work in the Northern Expedition. Yu Lexing used to be the Party branch secretary of the Ye Ting Independent Regiment, and his external status was the political instructor of the Regiment. After the Northern Expedition began, the Ye Ting Independent Regiment, with party member and League members as the backbone, was the vanguard of the whole army, invincible, and won the title of "Iron Army" for the fourth army, especially in the battles of Heshengqiao and Tingsiqiao, which were decisive battles with Wu, Ye Ting Independent Regiment was not afraid of sacrifice, and defeated the enemy in one fell swoop, becoming the first fighting force at the gates of Wuchang.
1927 1, the Ye Ting Independent Regiment was expanded, and the original backbone was 73 regiments. Yu Lexing stayed in the regiment and continued to serve as secretary of the General Party Branch. Later, when the domestic situation changed suddenly, Chiang Kai-shek and Wang Ching-wei rebelled openly, and Zhong * * * decided to launch an armed uprising in Nanchang. Yu Lexing took part in the uprising with the army and went south with the insurgents. In March, Yu Lexing was transferred to the Military Command Staff Committee under the leadership of the former enemy committee, and Chen Yi, who came from Wuchang, was sent to the 73rd regiment to take over the work. When Chen Yi reported to the regimental headquarters, Lin Biao, then the company commander of the regiment for seven years, also reported to the regimental headquarters, saying that the meals for seven consecutive months had been taken away by the orderly. In a rage, colonel Huang Haosheng wanted to shoot Lin Biao. As early as when he was studying in France, Yu Lexing, who was very familiar with Chen Yi, hurried out to make amends and suggested that Chen Yilai deal with the matter. Chen Yi persuaded the colonel to shoot the cadres easily with the imminent war, and Lin Biao saved his life.
When Nanchang Uprising troops arrived in Chaoshan, Guangdong Province, they were besieged by superior enemy forces and failed. At this critical moment, the determined revolutionaries did not flinch and continued their struggle, but Yu Lexing did a very disgraceful thing-he took the gold from the army and deserted. According to Yu Lexing's later letter to Zhou Enlai, he decided to leave the army privately because he saw that the army was breaking up and felt that it was meaningless to persist. Even "there was no plainclothes at that time, so he brought the plainclothes of the orderly". Then he left without saying goodbye on the grounds that Zhou Enlai was "seriously ill, sleeping under the hut, and his brother could not bear to bother my brother". At the same time, he still has a batch of gold sent by Li. It was not until Zhou Enlai came to Shanghai and called Yu Lexing to talk that Yu Lexing admitted that "the procedure was wrong and he should not have taken the gold away, and he was willing to accept the punishment of the school". But after writing this letter, Yu Lexing never contacted this China organization again and became a de facto defector.
After leaving the Party, Yu Lexing got another job. He founded China Automobile School at No.761Baylor Road (now Huangpi South Road) in French Concession, which is the first comprehensive automobile school in China. Yu Lexing, a mechanical major, has set up three majors for this school, which are divided into advanced mechanical classes, elementary classes and accelerated driving courses. The academic system of the first two classes is one year, while the accelerated driving course is three months. From the perspective of specialty setting, there are courses such as automobile science, mechanics, material science, electricity and mathematics. It was the only professional automobile school in China at that time. Later, some people touted the school run by Yu Lexing, saying that "China automobile started from now on". Although this is a bit excessive, this school has played a certain role in the spread of automobile technology in China. By 1930, the school had graduated from four advanced classes and five elementary classes, with more than 1,000 graduates, all of whom were assigned to various provinces to engage in automobile professional work.
1929, Yu Lexing was invited by Feng Yuxiang to go to the northwest to participate in the construction of Lanzhou. The following year, he was appointed as the deputy director of Shaanxi Machinery Bureau by Yang Hucheng. Shaanxi Machinery Bureau, named Machinery Bureau, is actually a large-scale arms enterprise established after Yang Hucheng presided over the political situation in Shaanxi, specializing in the production of guns and ammunition for Yang Department. Is a comprehensive enterprise established on the basis of several arsenals established by Feng Yuxiang during his stay in Shaanxi. Yang appointed Lian Ruiqi, who works in the General Political Department of the Northern Expeditionary Army, as the director, responsible for the preparatory work, and Yu Lexing as the assistant. For Yu Lexing, who majored in mechanical engineering, this place is useful for studying. However, due to the newly established machinery bureau and the inexperience of the host, in the preparatory work for more than one year, it costs 654.38+million yuan every month and can't produce 50,000 yuan of products. So in the second half of 193 1, Yang Hucheng took over from Lian Ruiqi as a director and took charge personally. Yu Lexing had to resign and return to Shanghai.