Cann't Nha Trang shells be brought back to China?

I can't. The Catalogue of Animals and Plants and Their Products Prohibited from Entering People's Republic of China (PRC) clearly stipulates that it is forbidden to bring high-risk animals and plants and their products such as ivory and unprocessed shellfish into the country. Therefore, when you come back from Vietnam with shells, you should pay attention to the customs regulations of China and avoid carrying contraband such as ivory, so as not to violate relevant laws and regulations.