The grinding concentration determines the friction between grinding medium and material, pulp fluidity, effective density and effective weight of medium, and then affects the production efficiency of vertical roller mill.  The grinding concentration also has a suitable range, which is too large or too small. In actual production, we generally advocate "high concentration grinding and low concentration classification".  Generally, the grinding concentration is comprehensively determined by material properties, grinding process conditions, classification efficiency and overflow concentration.  Taking the lattice vertical roller mill as an example, when coarse grinding (› 0.15mm), the grinding concentration should be controlled between 75 ~ 85%; When the overflow vertical roller mill is used to treat fine grinding products (0.10 ~ 0.074mm), the grinding concentration is generally controlled between 65 ~ 75%.