Objective: Analysis of infection rate of mycoplasma pneumonia(MP) in Nanjing and surrounding areas are made in order to probe into epidemic characteristics of MP infection in this area. At the same time it offers help for prevention and treatment of the disease. Methods: Child outpatients with respiratory infection from Nanjing or surrounding areas in Nanjing Children’s Hospital Affiliated to Nanjing Medical University from January 2008 to December 2010 were subject to serum MP passive agglutination method to test MP-IgM antibody. Statistical analysis of MP-IgM antibody test result based on clinical data was made. Results: 31843 serum samples were tested during the three years. Out of them 13166 samples were positive,MP-IgM antibody with the positive rate being 41.35%;The positive rate in 2008 was the highest covering 45.08% of the total child patients infected with respiratory diseases in a year;Positive rate of MP-IgM antibody of children whose age was below or equal to 1 years old was 9.90%;From 1 to 3 years old was 32.48%;From 3 to 5 years old was 38.24%;Over 5 years old was 57.57%;Positive rate of male child patients was 36.08% and female child patients was 48.16%;On the other hand,Positive rate in the spring was 39.56%;In the summer was 36.51%;In the autumn was 42.11%;In the winter was 48.69%. Conclusion: MP is the main causative pathogen for respiratory infection of children in Nanjing area. MP infection goes on throughout the year with infection rate in the winter being the highest;Infection rate of infants is the lowest while that of preschool children is the highest;Infection rate of female child patients is higher than that of male child patients. The result of this study uncovers the epidemic characteristics of MP infection in Nanjing and surrounding areas,which is of significance for prevention and treatment of MP in this area.