Objective：To assess the efficacy of middle dose of recombinant human growth hormone（rhGH） for children with idiopath－ic short stature（ISS）. Methods：Night-six ISS children（32 males and 64 females） were treated with middle dose of rhGH[0.35-0.42 mg/（kg·week）] before night sleeping for 1，２，3 years. Changes in height，growth velocity，mean height standard deviation score（ＨtS－DS），bone age，predicted adult height and side effect after treatment were measured every 6 months. Results：（1）During the three years’ treatment，the mean growth velocity increased from 4.46（4.07-4.68） cm/year to 11.00（9.25-12.5） cm/year，8.10（7.00-9.50） cm/year and 7.40（5.63－8.00） cm/year；mean HtSDS increased form -2.48[（-2.83）-（-2.25）] to -1.5[（-1.93）-（-1.17）]，-1.00[（-1.69）-（-0.58）] and -0.52[（-1.86）-（-0.13）];predicted adult height increased form 149.20（145.10-155.30） cm to 155.90（150.30－162.70） cm，159.00（154.00－162.70） cm and 160.05（153.18-166.80） cm（P<0.05）. （2）The growth velocity of ISS was significantly better at Tanner stage Ⅰ，Ⅱ，Ⅲ than at stage Ⅳ. （3）Changes in bone age were 1.10（0.80-1.30） years，1.10（0.83-1.20） years and 1.10（0.98-1.30） years（P >0.05）. During the treatment，a few had temporary blood sugar rises，no obvious side effects was observed except mild reaction in the injection site. Conclusions：The therapy with middle dose of rhGH for ISS children is effective in im－proving growth and increasing predicted adult height without affecting growth potential and side effect.