Abstract: The mathematical model of product particle size distribution of grinding process is established and predicted, which will be to the benefit of guiding mill grinding. Batch grinding experiments on Shizhyuan tungsten ores in different grinding time in the laboratory were made to show that particles conform to first order grinding kinetics when the particle size was no more than 0.1 millimeter, however, the particles conformed to n order grinding kinetics when the particle size was more than 0.1 millimeter. There was a power function relationship between the parameter k of first order grinding kinetics and diameter d, which distributed in function of R=R₀exp-(0.014 42+9.538 65d^{1.761 28})t; at n order grinding kinetics, the parameter k and diameter d were consistent with power function relationship, and the parameter n and diameter d were consistent with logarithmic function relationship, which distributed in function of R=R₀exp -(-0.134 1+1.151 42d^{0.681 69})t^{0.718 18-0.386 56lnd}. Through the comparison with theoretical values which were calculated by grinding kinetics equations with the grinding actual results, actual values had high degree of coincidence with it. Therefore the study establishes a theoretical basis for controlling the grinding product particle sizes by adjusting the feed quantity of mill and sand return of grader.