Objective: To investigate whether carotid intima-media thickness (CIMT) and carotid plaque are associated with cognitive impairment in patients with Parkinson's disease (PD). Methods: According to the Monterill Cognitive Assessment Scale, 225 PD patients were divided into three groups: normal cognitive function (NC) group(n=41), mild cognitive impairment (MCI) group (n=76) and dementia (PDD) group (n=108). The differences of clinical and carotid ultrasound indexes were compared, and the independent factors of PD cognitive impairment were analyzed by multiple linear regression. Results: The educational level of NC, MCI and PDD groups showed a downward trend (P < 0.05); H&Y rating, UPDRS-III, Hamilton Depression Scale, Pittsburgh Sleep Quality Index Scale, cystatin C level, CIMT, carotid plaque detection rate and carotid plaque vulnerability score showed an increasing trend (P < 0.05). Regression analysis showed that high education level (P < 0.001) was an independent protective factor for PD cognitive impairment, and CIMT thickness (P=0.002) and high H&Y (P=0.001) were independent risk factors for PD cognitive impairment. Conclusion: Carotid atherosclerosis was associated with cognitive impairment in PD patients.