Abstract: The number of holes in the net sand affects the effective grinding area, which affects the grinding performance of net sand. Polyester mesh cloth with different porosities was used as the backing of net sand, which was produced into net product after pre-treatment, the first layer resin, electrostatic coating, and the second layer resin. We study the influence of net backing cloth porosities in sanding car putty by observing clogging status during sanding, testing roughness of surface, and charaterizing the clogging condition of grid grinding surface through scanning electron microscope. The results show that for coarse grit sanding, the best porosity is 30%, and for the fine grit, the best porosity is 20%.