Parkinson’s disease (PD) is associated with gastrointestinal motility abnormalities that could favor the occurrence of small intestinal bacterial overgrowth (SIBO). The aim of the study was to assess the prevalence of SIBO in Chinese patients with PD and the potential impact of SIBO on gastrointestinal symptoms and motor function. 182 consecutive Chinese patients with PD patients and 200 sex, age, and BMI-matched subjects without PD were included. All participants underwent the glucose breath test to assess SIBO. We examined the associations between factors and SIBO with logistic regression using SPSS. Fifty-five of the 182 PD patients were SIBO positive (30.2 %; 95 % CI 23.5–36.9 %) compared with 19 of 200 in the control group (9.5 %; 95 % CI 5.4–13.6 %); the difference was statistically significant (P < 0.0001; OR 4.13; 95 % CI 2.34–7.29). Motor fluctuations present was higher in the PD patients with SIBO than in the patients without SIBO (70.9 vs. 45.7 %; P = 0.002). Multivariate analysis showed that disease duration, Hoehn and Yahr stage, Unified PD Rating-III score, Unified PD Rating-IV score, and Non-Motor Symptoms Scale score were the factors associated with the SIBO-positive status in PD patients. SIBO was highly prevalent in PD, and nearly one-third was detected. SIBO was associated with worse gastrointestinal symptoms and worse motor function. Further studies are needed to specify the reasons underlying SIBO and worse motor function in PD.