Typically, mycoplasma pulmonale is diagnosed if the single antibody potency is greater than 1:160. A quadruple increase in antibody potency during the recovery period compared to the initial period can also be diagnosed as mycoplasma infection. Since the immunity of children is not fully developed, the period from mycoplasma infection to antibody production sometimes cannot produce an immune response, i.e., it cannot produce IgM, so the IgM test at this time is slightly positive or decreasing, or even undetectable, and should be judged according to the patient’s physical condition, time of onset, and clinical symptoms, or further confirmed by other tests. Pulmonary mycoplasma assay, hospitals use more gelatin particle agglutination, also luminescence and enzyme-linked immunoassay, the current gold standard method is culture and nucleic acid method.