Abstract: The formula of cumulative weight percentage at different particle sizes, which was in the case of composite particle size distribution, was proposed. Based on analyzing the theoretical model of ultrasonic attenuation, the formula was integrated into the ultrasonic attenuation model, and the relation of ultrasonic attenuation to pulp density and particle size was derived. The correlation between ultrasonic attenuation and particle size distribution was given by combining experiments with data analysis, and an inverse parameters optimization method, genetic algorithm, was applied for particle size distribution. The result of inversely calculation shows that its precision is higher.