Based on chemiluminescence inhibition effect of toxoflavin on luminol-hydrogen peroxide-copper oxide nanoparticles system in alkaline medium, a novel method for monitoring toxoflavin potential emergency pollution in municipal drinking water was successfully developed. Combining with flow injection method, the chemiluminescence intensity of different mixed solutions was determined by ultra-weak chemiluminescence analyzer. Optimal conditions were obtained by the means of one-way tests among 4 factors. Based on the one-way tests result, a response surface experiment was conducted in order to acquire standard curve, detection limit and recovery of different water samples. The linear range for toxoflavin monitoring was 0.005~5.000 mg/L with a detection limit (LOD) of 0.001 mg/L and recovery of 84%~114%. The relative standard deviation (RSD) of addition of 0.05 mg/L toxoflavin was 0.28% (n=11). This method was rapid, convenient, operable and could be applied to on-line monitoring and emergency warning of potential emergency pollution of toxoflavin in municipal drinking water.