Objective：To study the relationship between the level of cerebrospinal fluid homocysteine（HCY） and the cognitive dys－function among patients with Parkinson’s disease（PD）. Methods：The basic information，disease situation and cognitive function of pa－tients with PD were investigated and lumbar puncture was performed to extract cerebrospinal fluid. The levels of cerebrospinal fluid HCY were determined by high performance liquid chromatography combined with fluorescence detection method. The correlation be－tween cerebrospinal fluid HCY levels and the cognitive function was assessed. Results：The scores of the mini mental state examina－tion（MMSE），montreal cognitive assessment（MoCA），rey auditory verbal learning test（RAVLT），symbol digit modalities test（SDMT） and the wechsler intelligence scale-block design（BD） all showed significant correlations with cerebrospinal fluid HCY in patients with PD after eliminating the bias of age，depression，course of disease，scores of unified Parkinson’s disease rating scale and Levodopa dosage. Conclusions：The elevated cerebrospinal fluid HCY level is significantly correlated with the cognitive dysfunction. The in－crease of cerebrospinal fluid HCY maybe one of the main important risk factors of PD patients’ cognitive dysfunction.