Objective To analyze the correlation between catechol-O-methyltransferase (COMT) gene polymorphism and cerebral vasospasm (CVS) in early period after subarachnoid hemorrhage (SAH). Methods The clinical data of 167 patients with spontaneous SAH, who were treated in our hospital from Jan. 2008 to Dec. 2008, were collected for this study. COMT genotyping was performed by means of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The degree of CVS was identified by transcranial Doppler (TCD). Hunt-Hess classification was used to evaluate the severity of the patients' condition. The bleeding amount was evaluated by means of Fisher classification of head CT. χ² test (SPSS13.0 software) and logistic regression were adopted to analyze the correlation of COMT gene polymorphism and other clinical data with early CVS after SAH. Results The distribution of each allele matched with Hardy-Weinberg law and the research samples were heredity equilibrium population. Early CVS incidence of patients with COMT A allele was significantly higher than those with COMT G allele (51.7% vs 38.5%, P<0.01). Early CVS incidence of patients with COMT A/A genotype was significantly higher than those with COMT G/G genotype (66.7% vs 35.9%, P<0.05). Univariate logistic regression demonstrated that COMT A allele, A/A genotype and Grade 3-5 of Hunt-Hess classification were all associated with early CVS. After adjustment of general information, further multivariate logistic regression demonstrated that COMT A allele, A/A genotype were the risk factors of early CVS after SAH. Conclusion COMT A allele and A/A genotype might be risk factors of early CVS after SAH.