Objective To use MRI susceptibility weighted imaging(MRI-SWI)to examine cerebral microbleeds(CMB)in elderly Parkinson's disease(PD)patients,and analyze the relationship be-tween CMB and cognitive impairment in them.Methods A prospective cohort study was conduc-ted on 80 elderly PD patients admitted to Huai'an No.3 People's Hospital from June 2020 to April 2024.All patients underwent MRI-SWI examination and PD-Cognitive Rating Scale(PD-CRS).According to the results of MRI-SWI examination,they were divided into a CMB positive group(17 cases)and a CMB negative group(63 cases),and based on the results of PD-CRS,they were also assigned into a cognitive impairment group(34 cases)and a normal cognitive group(46 ca-ses).General clinical data were compared between the CMB positive and negative groups,and be-tween the cognitive impairment group and normal cognitive group.CMB type and severity were compared between the cognitive impairment group and the normal cognitive group.Multivariate logistic regression analysis was applied to investigate the relationship between CMB and cognitive impairment in elderly PD patients.Results The CMB positive group had longer PD course,ad-vanced Hoehn Yahr(H-Y)late stage,higher unified Parkinson's disease rating scale(UPDRS)Ⅰscore,and larger ratio of cognitive impairment than the CMB negative group(P＜0.05,P＜0.01).The proportion of cognitive impairment in patients with lobular CMB was higher than that in deep-subtentorial CMB and mixed patients,and the proportion of cognitive impairment in patients with severe CMB was higher than that in patients with mild and moderate CMB(P＜0.05).Multivariate logistic regression analysis showed that the occurrence of cognitive impairment in elderly PD patients was related to the course of disease,H-Y mid stage,H-Y late stage,CMB,and UPDRS Ⅰ score,which may be risk factors for cognitive impairment(OR=1.356,95％CI:1.121-1.640;OR=16.585,95％CI:2.532-108.623;OR=5.786,95％CI:1.073-31.206;OR=6.553,95％CI:1.066-40.281;OR=2.102,95％CI:1.384-3.194).Conclusion The coexistence of CMB in elderly PD patients can increase the risk of cognitive impairment,with a higher risk of cognitive impairment in cerebral lobe CMB and severe CMB.Therefore,early detection is crucial.