Abstract: OBJECTIVE To investigate the effect of Helicobacter pylori infection（HP） on coagulation function and platelet mitochondrial Complex I activity in patients with Parkinson’s disease. METHODS Totally 103 patients with Parkinson’s disease admitted to Wuhan Central Hospital Affiliated to Tongji Medical College from Dec. 2016 to Dec. 2018 were selected as the study subjects, and divided into 79 cases of infection group and 24 cases of non-infection group according to whether they were infected with HP or not. The prothrombin time（PT）, thrombin time（TT）, activated partial thrombin time（APTT） and fibrinogen（Fib） were measured by SysmexCA 2500 automatic coagulation instrument and matching kit, and the activity of platelet mitochondrial Complex I was determined by spectrophotometry. RESULTS There was no significant difference of PT between the two groups（P=0.496）. The TT and APTT of the infection group were（15.89±0.46）s and（26.32±0.89）s, respectively, significantly lower than those of the non-infection group, and the Fib（3.98±0.24 g/L） was significantly higher than that of non-infection group（P＜0.05）. The mitochondrial Complex I activity of the infection group was（1.23±0.28） U/ml, significantly lower than that of the non-infection group（P＜0.05）. The UPDRS III score and the UPDRS IV score of the infection group were（28.40±1.79） points and（3.41±0.37） points, respectively, higher than those of non-infection group. There was no significant difference of the Hoehn-Yahr classification between the two groups（P=0.619）. CONCLUSION Abnormal coagulation function and mitochondrial dysfunction caused by HP infection may be involved in the occurrence of Parkinson’s disease, which is worthy of clinical reference.