Ore harness reflect its own mineral constitute and physical & mechanical performance, which is unchangeable. Ore with compact structure, small crystals and high hardness is hard for Raymond mill of grinding. These ores will waste a long time in Raymond mill processing to achieve the required product fineness, which effect the handling of Raymond mill. While the low hardness ore with developed cleavage is too easy for grinding with comprehensive higher output capacity of Raymond mill. Due to the unchangeable of ore hardness, staff should take a positively attitude to deal with higher hardness ore. For example, staff can find the most proper ore ejecting density and sand returning quantity, etc operation situation. The ore from the crushing system is under the situation of reduced granularity as possible. Then find the best ratio in stead particle situation.