Objective　To examine the preventive effect of magnesium sulfate on hypertension caused by ACTH in the treatment of infantile spasms (IS). Methods 46 children diagnosed as IS were recruited from two hospitals during May, 2011 to October, 2013.23 patients in group A (treatment group) were treated with magnesium sulfate and ACTH in hospital A;another 23 cases in group B (control group) were treated with ACTH only in hospital B. The therapy course was 2 weeks. Results Hypertension was not observed in the treatment group, while 6 children were observed with hypertension in the control group. There was significant difference between the two groups (P<0.05). Conclusions Magnesium sulfate could prevent the incidence of hypertension in the treatment of IS with ACTH, and benefit the completion of treatment course.