Abstract: By supposing lump coal output obeying exponential distribution, Weibull distribution and uniform distribution, The mathematical model of it is set up. The granularity of 5~15,15~25 and 25~50mm while the shear is working is simulated by simulating software. The simulation result is compared with its experimental value and the optimal distribution is found out which provide a theoretical basis for determining resonablly lump coal output.