The hardness of acrylic plate is one of the parameters that can best reflect the production process and technology of casting acrylic plate, and it is an important part of quality control. The hardness can reflect the purity of raw material PMMA, the weather resistance of the plate and the high temperature resistance. Hardness directly affects whether the plate will shrink, bend and deform, and whether the surface will crack during processing. Hardness is one of the hard indexes to evaluate the quality of acrylic board. The average Mohs hardness is about 8 and 9 degrees.