Abstract: To improve the photo-catalytic degradation efficiency of organic phosphorus pesticide, taking acephate as a model pollutant, the effects of light source species, reactor configuration and materials, and the way of combining illuminator with the reactor on the degradation efficiency were investigated. A photo-catalytic reactor was developed and tested. The results indicated that the optimized reactor was with inside illuminated photo-catalytic reactor composed of quartz glass and light source of 450 W high-pressure mercury lamp with dominant wave length of 365 nm, which was favorable for the photo-degradation of acephate. The degradation rate of 16 mg/L acephate in the optimized reactor with 0.1 g/L titanium dioxide dose for 60 min was 96.55%. This research provides a reference for the optimization of the photo-catalytic degradation reactor used for organic phosphorus pesticide.