Abstract: To enhance the defect prediction ability, an improved Rayleigh model considering the factor of incorrect repair is presented. The shortcoming of the traditional Rayleigh defect prediction model was analyzed. The improved Rayleigh defect prediction model was established based on the consideration of the incorrect repair factor. The parameters of the improved model were obtained by using experience values and maximum likelihood estimation. Experimental verification shows that the improved model can effectively enhance the similarity between the prediction values and actual ones.