Objective To investigate the association of the effect of modified electroconvulsive therapy with polymorphism of rs326174 loci in ADCY-2 gene in Chinese patients with bipolar disorder. Methods A total of 100 patients with bipolar disorder（ BPD） were distributed into MECT group and non MECT group by random number table method with 50 cases in each group. The polymorphism of rs326174 loci in ADCY-2 gene was detected by TaqMan genotyping. The efficacy was evaluated by the General Rating Scale（GAS）. The results were statistically analyzed. Results There was no difference in genotype distribution between the two groups. A and C alleles were both detected in two groups. There were three genotypes： AA， AC and CC. At baseline， there was no statistically significant difference in GAS score between the two groups（ P＞0.05）， while GAS score in group MECT were significantly higher than those in non MECT group at the first weekend， the second weekend and the fourth weekend after treatment（ P＜ 0.05）. In the MECT group， there was no statistical difference in the GAS score among the three genotypes of patients before treatment and the fourth weekend after treatment （P＞ 0.05）. At both end of the first and second week， the score of GAS in three genotypes from high to low were AA， AC and CC genotype， and the difference was statistical significant（ P＜0.05）. Conclusions MECT is an effective method for the treatment of bipolar disorder. The polymorphism of ADCY2 gene may be associated with efficacy of MECT.