Abstract: Objective：To explore the level of serum leptin in patients with Parkinson disease (PD) and the related influence factors. Methods：A total of 114 patients with PD were enrolled into the experimental group, and 55 healthy individuals were selected as the control group. The serum leptin level was detected by enzyme-linked immunosorbent assay (ELISA). The level of serum leptin and its influencing factors were evaluated by univariate and multivariate logistic analysis. The correlation between serum leptin level and duration and severity of the PD disease were explored by Spearman analysis. Results：The serum leptin level in PD group was (5.43±1.93) g/L and lower than that in the control group (t=-24.606，P<0.000). Multivariate logistic analysis and Spearman analysis showed that PD duration (OR=0.567, r=-1.783,P=0.002), PD severity (OR=0.203,-0.422, P=0.003), and body mass index (BMI; OR=4.369, r=0.768, P=0.000) were correlated with the serum leptin level. Conclusions：The serum leptin level is lower in patients with PD, which might be positively correlated with the duration and severity of disease, while negatively correlated with the BMI.