Abstract: case with respiratory tract infection and penumonia as well as 76 health children's serum were tested by MPIFA which was from American zeus scientific Inc. Results show that positive rate of MPIgM, IgG in respiratory tract infection was 23% and l3% res pectively, both positive rate is 6.0%,total positive rate was 30%;positive rate of MPIgG in Health children was 5.22%. The infomtation of 25 MP identited by laboratory and clinic in hospital was analyzed.The aystem were various. 80% of case had persistent cough, 48% had fever, the white blood cell in most case were in nomal level.72% case had pneumocystis by X ray, which show early then signs of lung.In clinic it not easy find the diffents from other repiratory virus infection and pneumonia diserse. The used in clinic identited that method is special, sensitive, easy and fast. It can early and fast diagnose MP. It offers a fast serum method for MP clinic diagnose and epidemiology investigation.