Blood sampling is mainly to check for antibodies to the new coronavirus, but it cannot confirm the diagnosis. New coronavirus is a new type of coronavirus, which is highly infectious and pathogenic. After entering the human body, it not only causes new coronavirus pneumonia, but also has an immune reaction with the human body and produces corresponding antibodies in the human blood. There are two main types of antibodies to the new coronavirus, including IgG and IgM antibodies, and the presence of the new coronavirus infection can be determined by drawing blood for these two antibodies. If the blood is positive for IgM antibodies, it is more likely that there is an acute infection. If the blood is positive for IgG antibodies, it only indicates a previous infection with the new coronavirus, but not necessarily a current infection. A combination of other test results, including IgM and nasopharyngeal swab nucleic acid testing, is needed. Antibody testing for neo-coronavirus has limitations and the possibility of false negatives, so a combination of nucleic acid testing is often needed to confirm the diagnosis.