Objective Cognitive impairment is one of the most serious non-motor symptoms of Parkinson’s disease (PD), and appears even in early stage of the disease. Our study aimed to analyze the association of catechol-O-methyltransferase (COMT) polymorphism and related factors with cognitive impairment in Chinese PD population. Methods A total of 1 087 Chinese PD patients were recruited by Chinese Parkinson Study Group (CPSG) from 29 research centers throughout all over the country. They were divided into cognitive impairment group (n＝385) and non-cognitive impairment group (n＝702) according to their medical history and clinical data. COMT genotype was sequenced. Chi-square test and Fisher’s exact test were used to analyze the association between cognitive impairment and COMT polymorphism, and binary logistic regression model was used to screen the risk factors for cognitive impairment. Results There were no significant differences in the genotype and allele of the objective gene between the two groups (P＞0.05). Logistic regression analysis showed that age at onset, Hoehn-Yahr score, and Unified Parkinson’s Disease Rating Scale (UPDRS) Ⅲ score were positively correlated with cognitive impairment. The PD patients with older age at onset, higher scores in Hoehn-Yahr scale and UPDRS Ⅲ were prone to have cognitive impairment. Conclusion Cognitive impairment is related to the age at onset and severity of the disease.