Is it legal for the US delegation to deliver food without a health certificate?

Illegal. According to the inquiry of People's Republic of China (PRC) Food Safety Law. The production, processing, storage and transportation of food need to comply with the Food Safety Law and need a health certificate. The delivery of food by Meituan is a part of food transportation. Therefore, the US Mission does not apply for a health certificate, and it is illegal to deliver meals. Health certificate refers to the proof of preventive health examination, which proves that the examinee has the health quality to engage in the prescribed business.