Abstract：Objective To investigate the mechanism and clinical efficacy of vitamin D combined with Xiyanping in the treatment of infantile pneumonia. Methods A total of 140 pediatric patients with pneumonia in our hospital from 2020 to 2022 were randomly assigned to an observation group and a control group, with 70 patients in each group. The control group received antibiotic therapy combined with Xiyanping injection, while the observation group was treated with vitamin D soft capsules in addition to the therapy administered to the control group. The primary outcomes were the overall clinical efficacy rate, serum procalcitonin （PCT）, and high-sensitivity C-reactive protein （hs-CRP） levels. Results Following treatment, the overall clinical efficacy rate in the observation group was significantly higher than that in the control group, with a statistically significant difference （χ2＝6.813, P＜0.05）. Serum PCT and hs-CRP levels in the observation group were also significantly lower than those in the control group, with a statistically significant difference （t＝8.578, 17.110, both P＜0.05）. Conclusion The combination of vitamin D and Xiyanping injection is highly effective in the treatment of pediatric pneumonia, potentially due to its role in modulating and enhancing the immune response.