Objective To explore the changes of humoral immune and cellular immune function indexes in children with bronchial asthma complicated with mycoplasma pneumonia (MP) infection, so as to provide guidance for its clinical diagnosis, prevention and treatment. Methods 120 children with bronchial asthma admitted to Wujiang District Children's Hospital of Suzhou from December 2019 to April 2021 were selected as the observation group. According to the expression level of plasma MP antibody (MP-IgM), they were divided into the MPIgM positive group (67 cases) and the MP-IgM negative group (53 cases), and 60 children who underwent physical examination during the same period were selected as the control group to carry out a prospective study. Compared the MP-IgM positive group and the MP-IgM negative group of children with immunoglobulin levels, T lymphocyte subsets levels and T-helper lymphocyte type-1/T-helper lymphocyte type-2 (Th1/Th2) ratio between the control group and the observation group. Results The levels of serum immunoglobulin A (IgA), immunoglobulin G (IgG) and immunoglobulin M (IgM) of children in the observation group were significantly higher than those in the control group; ande the MP-IgM positive group was significantly higher than the MP-IgM negative group; the CD3+ , CD4+ percentage,CD4+ /CD8+ ratio, Th1/Th2 ratio of children in the observation group were significantly lower than those in the control group; and the MP-IgM positive group was significantly lower than the MP-IgM negative group (all P < 0.05). Conclusion Most children with bronchial asthma have immunoregulatory dysfunction, immunoglobulins show an abnormally elevated trend, T lymphocyte activation function begins to weaken, and cellular immune function impaired , and this manifestation is more pronounced in children with bronchial asthma complicated with MP infection.