Objective To discuss the optimal time for operation in patients with malignant middle cerebral artery (MCA) syndrome. Method The relation between effectiveness and operating time was analyzed in 47 patients to compare the effects of early and delayed operation by SPSS10.0. Results Among 27 patients undergoing early operation, 18 were cured or restored, 4 seriously disabled and 5 died. While among 20 patients undergoing delayed operation, only 9 were cured or restored, 4 seriously disabled and 7 died. The prognosis of delayed operation group was worse than that of early operation group. Conclusions Selecting the optimal time to operate may decrease the mortality and morbidity of MCA syndrome.