Abstract: Objective:To investigate the effects of de-escalation treatment of antibiotic on the serum vitamin D in children with severe asthmatic.Methods:One hundred and ninety children with severe asthmatic were randomly divided into the treatment group and control group according to the random draw principle(95 cases each group).The control group and treatment group were treated with routine antibiotic and de-escalation of antibiotic for 7 days,respectively.Results:The total effective rate in treatment group(97.9%) was significantly higher than that in control group(88.4%) (P<0.01).The disappearance time of wheezing and pulmonary rale,and hospitalization time in treatment group(3.14±0.34) d,(4.63±0.45) d and(9.39±3.22) d were significantly less than those in control group(4.22±0.45) d,(7.82±0.56) d and(11.45±2.95) d,respectively(P<0.01).The levels of serum vitamin 25(OH) D in treatment group and control group after treatment(53.24±9.45) ng/mL and(45.39±10.22) ng/mL were significantly higher than those before treatment(28.24±9.33) ng/mL and(28.11±8.97) ng/mL,respectively(P<0.01),and the increasing degree of which in treatment group was higher than that in control group(P<0.01).Conclusions:The de-escalation treatment of antibiotic in children with severe asthmatic can increase the serum vitamin 25(OH) D content,improve the overall treatment effect,and promote the rehabilitation of children.