Abstract: Lowpurity hematite was crushed with high pressure grinding roll， and effects of operating factors such as roller surface pressure and speed， and ore moisture content on size of crashed products were studied. With the increase of roller surface pressure， the overall size became smaller， and size of products crushed in the roller center was distributed more concentratedly， while at the roller edge was more evenly. The products in the center became finer when the roller speed was increased into certain range， however， if further accelerating speed， no size change was observed. Roller speed had no obvious effect on the product size at edge. When the ore moisture content was increased， no obvious change was detected in product fineness. The product size distribution in the center was more concentrated， while at the edge it was more even.

Key words: high pressure griding roll, roller surface pressure, roller surface speed, moisture content of the ore, lowgrade hematite, product size