Objective: To analyze the differentially expressed genes in peripheral blood mononuclear cells (PBMCs) of asthmatic children before and after subcutaneous immunotherapy (SCIT), with the aim of screening potential biomarkers. Methods: This study collected clinical data and PBMCs from asthmatic children before and after treatment, and divided them into a differential gene screening group (7 cases) and a differential gene validation group (30 cases) for preliminary screening and subsequent validation, respectively. Transcriptome differential analysis was performed on PBMCs samples from 7 asthmatic children before and after treatment using RNA sequencing technology. After preliminary screening, candidate genes were validated by qReal-time PCR in the baseline group and the 16-week treatment group of 30 children undergoing SCIT. Spearman correlation analysis was used to investigate the correlation between the expression levels of candidate genes and clinical and pulmonary function indicators, and the biomarker efficacy was evaluated using ROC curves. Results: In the differential gene screening group, a total of 317 differentially expressed genes (166 upregulated and 151 downregulated) were identified in the 16-week SCIT group compared to the baseline period. qReal-time PCR validation revealed that the expression of SERPINB2 gene was significantly decreased after treatment compared to the baseline group (p < 0.05). Spearman correlation analysis indicated a significant correlation between the gene expression changes and reduced ACQ scores, CSMS scores, and increased C-ACT scores; the ROC curve suggested that this gene had good efficacy evaluation and predictive value. Conclusion: SERPINB2 expression was significantly downregulated after 16 weeks of SCIT treatment and was closely correlated with clinical improvement, suggesting that SERPINB2 could serve as a potential biomarker for evaluating the efficacy of SCIT in pediatric asthma, but further experimental validation is required.