Trading companies can legally purchase agricultural products, but they need to abide by relevant laws and regulations. According to "Regulations on the Management of Agricultural Products Circulation in People's Republic of China (PRC)" and other laws and regulations, trading companies need to have corresponding qualifications and conditions, such as business licenses and tax registration certificates, in order to operate legally. At the same time, trading companies should abide by market rules and the principle of fair trade when purchasing agricultural products, and must not engage in unfair competition or harm farmers' interests.