Objective To investigate the relationship between the infection rate of Mycoplasma pneumoniae (MP) and age, sex and season. Methods Passive agglutination assay was used to detect Mycoplasma pneumoniae antibodies (MP-Ab) in the serum of patients with respiratory tract infection, and MP-Ab test results in 2010 were analyzed. Results The positive rates of 5 year test results were 30. 10% ;among the results, the positive rates of male and female patients were respectively 30. 74% and 36. 12% ,the difference was statistically significant ( P < 0.05 ) ; And every age group were significantly different ( P <0. 001 ), among each group, the positive rate of 3-14 years old patients was the highest; the season was no significant difference in incidence rates; the patients of positive tiler > 1:640 accounted for 10. 18% of the patients. Conclusion MP infection is increasing year by year, children aged 3 to 14 has become the highrisk groups. Women are more susceptible to MP than the men and the chances of infection are throughout the year, hut the most of the patients have a good prognosis.