Abstract: Objective To study the therapeutic effect and safety of different dosages of vitamin D₃ （1 400 IU/day vs 1 000 IU/day） combined with calcium on children with new-onset and infrequently relapsing nephrotic syndrome （IFRNS）. Methods Totally 64 children with new-onset nephrotic syndrome （n=12） or IFRNS （n=52） were selected and randomly divided into two groups.In group A,32 children were treated with vitamin D₃ （1 400 IU/day） combined with calcium （500 mg/day） on the basis of glucocorticoid therapy.In group B,32 children were treated with vitamin D₃ （1 000 IU/day） combined with calcium 500 mg/day on the basis of glucocorticoid therapy.The level of serum 25-hydroxyvitamin D （25-OHD）,serum calcium,parathyroid hormone,24-hour urine protein and plasma albumin in two groups were detected before and after treatment.The side effects and the rates of infection in the period of treatment were recorded. Results At one month and three months after treatment,the percentage increase in serum 25-（OH）Din group A was significantly higher than that of group B at the same time point （P<0.05）,but the percentage increase in serum calcium and parathyroid hormone in the two groups showed no significant difference （P>0.05）.Excluding the infection cases,the level of 24-hour urine protein was lower in group A than group B at three months after treatment （P<0.05）,while the level of plasma albumin was higher in group A than group B at three months after treatment （P<0.05）.There was no significant difference in rates of infection between group A and group B （P>0.05）.No adverse event,such as Vitamin D poisoning or hypercalcemia,were found in the two groups. Conclusion Vitamin D₃ （1 400 IU/day） combined with calcium （500 mg/day） in children with new-onset and infrequently relapsing nephrotic syndrome is more effective than vitamin D₃ （1 000 IU/day） combined with calcium （500 mg/day）,without adverse reactions.