Abstract: OBJECTIVE To investigate the effects of alfacalcidol on immun function and clinical efficacy in children with henoch-schonlein purpura (HSP). METHODS Sixty cases of HSP were selected and randomly divided into the alfacalcidol treatment group and the conventional treatment group, 30 cases in each group. The conventional treatment group was given the routine therapy, while the alfacalcidol treatment group was added alfacalcidol oral on the basis of the routine therapy. The peripheral frequence of Th17 cell and Treg cell of all the objects (before treatment and after 1 month treatment) were detected, and the serum concentrations of 1,25- (OH)₂ D₃, IL-10, IL-17 and MMP-9 were also detected. The clinical efficacy and symptom control time were compared between two groups. RESULTS Compared with pre-treatment, the proportion of Th17 cell were decreased significantly and the proportion of Treg cell were increased significantly after treatment, all those difference were significantly (P<0.01). The alfacalcidol treatment group had a significant change compared with the conventional treatment group. After treatment, the serum of 1,25- (OH)₂ D₃ in the alfacalcidol treatment group was higher than the convntional treatment group (P<0.01), while the serum of IL-10, IL-17 and MMP-9 levels were significantly reduced (P<0.01). The alfacalcidol treatment group was superior to the conventional treatment group in abdominal pain, joint swelling and pain, renal lesion regression time and recurrence times within half a year (P<0.05). CONCLUSION Alfacalcidol can improve the immune function of children with HSP, and it has a certain clinical efficacy, but more research is need to prove.