Immunoglobulin M (IgM) is the main component of immunoglobulin in serum, accounting for about 75% of the total immunoglobulin content in serum. IgM is the most important antibody in the body, which has anti-virus, neutralizing virus, antibacterial and immunomodulatory functions. Detecting the content of immunoglobulin in the body can understand the humoral immune function of the body, and help diagnose many diseases such as immune hyperplasia, immune deficiency, infection and autoimmune, which has important clinical significance.