Objective To explore the clinical effect of medopa combined with selegiline hydrochloride in the treatment of patients with Parkinson's disease and its impact on adverse reactions. Methods A total of 96 Parkinson's disease patients from January 2018 to December 2020 were selected and divided into two groups by the odd and even number drawing method, 48 cases each. The control group was treated with medopa, and the observation group was treated with selegiline hydrochloride on the basis of the control group. Then the clinical efficacy of the two groups were compared, and the Unified Parkinson's Disease Rating Scale was used to access the mental state, motor function and daily activity scores of the patients, and the incidence of adverse reactions was recorded. Results The total effective rate of the observation group was higher than that of the control group (87.50% vs 66.66%), with statistical significance(χ²=5.897,P=0.015). After treatment, the scores of mental state, motor function and daily activities were lower (P<0.05), and the scores of the observation group were significantly lower than those of the control group (t=8.250, P<0.001; t=4.388, P=<0.001; t=3.207, P=0.002);the incidence of adverse reactions had no differences (10.41% vs 12.50%, χ²=0.103, P=0.749). The adverse reactions were transient, which could be alleviated by drug withdrawal or rest. Conclusions Madopa combined with selegiline hydrochloride had a good clinical effect in the treatment of patients with Parkinson's disease. It could significantly improve the mental state, motor function and daily life of patients, with less adverse reaction, which is worthy of promotion.