【Abstract】 Objective To explore the relationship between the levels of lymphocyte subsets, Creactive protein (CRP) and vitamin D3 in peripheral blood and recurrent respiratory tract infection in children. Methods A retrospective analysis was made of 109 children with recurrent respiratory tract infection admitted to our hospital from January 2018 to December 2018 as the observation group. 100 healthy children in the same period were selected as the healthy group. The levels of CRP, vitamin D3, immunoglobulin and lymphocyte subsets were compared between the two groups. The correlation among lymphocyte subsets, CRP and vitamin D3 in peripheral blood was analyzed. Results The serum CRP level in the observation group was significantly higher than that in the healthy group (P＜0.05), and the serum vitamin D3 level in the observation group was significantly lower than that in the healthy group (P＜0.05). Compared with the healthy group, the level of immunoglobulin in the serum of the observation group decreased significantly (P＜0.05). The levels of CD3+, CD4+ and CD4+/CD8+ in the observation group were lower than those of the healthy group, the difference was statistically significant (P＜0.05). CD3+ and CD4+ were negatively related to CRP (r=-0.635, -0.348; P＜0.05). There was a positive correlation between CD 3, CD 4 and vitamin D 3 (r=0.367, 0.455; P＜0.05). CRP was negatively correlated with vitamin D3 (r=-0.319; P＜0.05). Conclusion The levels of RP, vitamin D3 and lymphocyte subsets in peripheral blood can be used to evaluate the changes of children with recurrent respiratory tract infection, which is of great guiding significance for the development of later treatment plan.