Abstract: An improved size-mass balance model based on batch-grinding experiment was proposed to predict the particle size distribution of industrial ball mill,which had the characteristics of high nonlinearity,time-delay and operation conditions changing.The breakage-rate model was improved based on the batch-grinding results that some certain size particles did not meet first-order breakage kinetics.Considered the influence of operating conditions,a LSSVM model between the parameters of the ball-mil model and the operating conditions was trained,so that the parameters of breakage rate model could be determined by grinding conditions.Simulation results show that the accuracy of this model is good enough and meets the needs of practical production.