Objective：To construct a screening model for monoamine oxidase（MAO） inhibitors in the treatment of neurodegenerative diseases. Methods：Benzylamine and 5-hydroxytryptamine（5-HT） were used as MAO-B and reaction substrates and their activities were measured by UV spectrophotometry，respectively. MAO concentration，substrate concentration，phosphate buffer concentration and pH，reaction time and temperature were optimized. Results：The optimized reaction system conditions were obtained as follows：under the conditions of enzyme pre-incubation time of 20 min and reaction time of 60 min at the temperature of 37 ℃，optimum con－dition for determination of MAO-B activity was 100 mmol/L phosphate buffer（pH 7.6） and 0.15 mg/ml MAO and 2.00 mmol/L ben－zylamine，optimum condition for determination of MAO-A activity was 100 mmol/L phosphate buffer（pH 7.4） and 0.40 mg/ml MAO and 5.00 mmol/L 5-HT. Conclusions：A screening model for monoamine oxidase inhibitors in vitro is constructed successfully. Due to its low cost and simple operation，it is suitable for large-scale screening MAO-B and MAO-A inhibitors.