Abstract：Objective：To observe the clinical efficacy of Jinzhen Oral Liquid combined with Acetylcysteine in the treatment of Mycoplasma pneumoniae pneumonia （MPP） and its effect on serum levels of cytokine-like protein 1 （CYTL1） and soluble B7 homolog 3 （sB7-H3） in children. Methods：A total of 120 children with MPP admitted to Nanyang Central Hospital from March 2023 to March 2025 were selected and divided into the control group and the combination group according to the random number table method，with 60 cases in each group. The control group was treated with Acetylcysteine， and the combination group was treated with Jinzhen Oral Liquid combined with Acetylcysteine. The clinical efficacy， symptom resolution time， and incidence of adverse reactions were compared between the two groups. The changes in immune function，serum levels of CYTL1，sB7-H3，and high-sensitivity C-reactive protein （hs-CRP） before and after treatment were also compared between the two groups. Results：The total clinical effective rate was 93.33% （56/60） in the combination group and 78.33% （47/60） in the control group， the difference being significant （P＜0.05）. The resolution time of fever，cough，rales，and wheezing in the combination group was earlier than that in the control group，differences being significant （P＜0.05）. After treatment，the levels of immunoglobulin M （IgM） and immunoglobulin G （IgG） in both groups were decreased when compared with those before treatment （P＜0.05），while the levels of CD3+ and CD4+ were increased （P＜0.05）；the levels of IgM and IgG in the combination group were lower than those in the control group （P＜0.05），and the levels of CD3+ and CD4+ were higher than those in the control group （P＜0.05）. After treatment， the levels of CYTL1， sB7-H3， and hs-CRP in both groups were decreased when compared with those before treatment （P＜0.05）， and the levels of the above three indicators in the combination group were lower than those in the control group （P＜0.05）. The incidence of adverse reactions was 16.67% （10/60） in the control group and 25.00% （15/60） in the combination group， there being no significant difference between the two groups （P＞0.05）. Conclusion： Jinzhen Oral Liquid combined with Acetylcysteine is effective in treating MPP. It can accelerate the relief of symptoms， improve the immune function of children，reduce the serum levels of CYTL1，sB7-H3，and hs-CRP，alleviate inflammatory response，and has high safety.