Objective To investigate the detection value of the positive rate of MP-IgM in children with Henoch-Schonlein purpura (HSP).Methods 80 HSP patients were chosen as the research subjects (the observation group),the other 40 healthy children were chosen as research subjects(the control group).The positive rate of MP-IgM,and positive changes in immune function of children with HSP combined with MP-IgM were analyzed in two groups.Results 32 cases were MP-IgM positive in the observation group,the positive rate was 40％.The MP-IgM positive rate in the observation group was significantly higher than that in the control group(P ＜0.05).The percentage of CD4+ in the observation group was significantly lower than that in the control group,the percentage of CD8+ was significantly higher than that in the control group,CD4+/CD8+ was significantly lower than that in the control group,NK was significantly lower than that in the control group(P ＜0.05).The percentage of CD8+ in MP-IgM positive group was significantly higher than that in the negative group,the percentage of CD4+/CD8+ was significantly lower than that in the negative group,the percentage of NK was significantly lower than that in the negative group (P ＜ 0.05).Conclusion MP infection is an important cause of HSP,it can aggravate the immune dysfunction and play an important role in the occurrence and development of HSP.