Abstract: In order to obtain a high reliable mathematical model of mill utilization coefficient with medium filling rate，material to grinding medium ratio，grinding time under small test work，grinding test was designed using Design-Expert 8.0 software，and the results were made model fitting and vertification.The results showed that single-factor influencing the mill utilization coefficient is weakened by grinded material to grinding medium ratio > medium filling rate > grinding time.Its interaction′s effect on the mill utilization coefficient are weaked as medium filling rate & material to grinding medium ratio > material to grinding media ratio & grinding time> medium filling rate and grinding time.Mill utilization coefficient reaches maximum，predictively at 0.298 t/(m³·h)，with medium filling rate of 35.79%，material to grinding medium ratio of 1.12 and grinding for 42.09 min.The predicting parameters of mill utilization coefficient derived from Design-Expert 8.0 closely approached the test results，which means that Design-Expert 8.0 software can be used to design and optimize grinding test quickly，efficiently and accurately.

Key words: Design-Expert 8.0, Filling ratio, Ratio of material to grinding media, Grinding time, Mathematical model