Objective To assess whether low dose corticosteroid could improve muscle strength and motor function in children with Duchenne muscular dystrophy ( DMD) .Methods In this randomized double-blind con-trolled trial , patients with DMD at the age of 5-10 diagnosed from September 2005 to December 2008 in Peking Union Medical College Hospital were enrolled .The patients were divided into treatment group and control group randomly.The treatment group was given prednisone at a dosage of 0.75 mg/(kg· d) for three months, and the control group was given vitamin C 0.3 mg/d as placebo in the same period .Every patient was followed-up once a month for a total of 4 times, testing muscle strength , motor function ( 9-meter walk test ) , respiratory function [forced vital capacity (FVC)], and serum creatine kinase .Results Thirty-one eligible DMD patients were en-rolled, including 17 in the treatment group and 14 in the control group.The mean muscle strength scores of the con-trol group at the 4 clinic visits were 38.2 ±7.5, 37.0 ±8.0, 36.2 ±7.6, and 36.6 ±7.7, while those of the treat-ment group were 37.7 ±6.1, 39.1 ±6.4, 40.3 ±5.9, and 40.0 ±5.6, respectively .The changes in muscle strength scores at 1, 2, 3 months after treatment compared with the scores at diagnosis were all significantly larger in the treatment group than in the control group (P=0.024, P=0.000, P=0.002).The mean time of 9-meter walk at the 4 visits in the control group were (7.7 ±2.5), (7.6 ±2.8), (8.1 ±2.4), and (7.6 ±2.8) s, and those in the treatment group were (8.5 ±3.4), (7.2 ±3.3), (7.6 ±3.1), and (7.1 ±2.8) s, showing signifi-cantly larger changes of time in the treatment group than in the control group at 2 and 3 months after treatment com-pared with the time at diagnosis ( P=0.013, P=0.003) .The four mean FVCs in the control group were (1.24 ± 0.28), (1.13 ±0.26), (1.21 ±0.31), and (1.16 ±0.26) L, and the mean FVCs in the treatment group were (1.14 ±0.37), (1.40 ±0.35), (1.42 ±0.36), and (1.52 ±0.37) L, showing significantly larger changes in the treatment group than in the control group at 1, 2, and 3 months after treatment compared with the FVCs at diag-nosis (P=0.000, P=0.006, P=0.000).The decrease of creatine kinase in the treatment group was significantly larger after 1-month treatment than that in the control group (P=0.035).There were no serious adverse effects in the treatment group except weight gain .Conclusions Short-term application of low dose prednisone in children with DMD can increase muscle strength , improve motor and respiratory functions .