Abstract The purpose of this paper is to investigate the effect of the diamond grain size, the wheel rotation speed, the table rotation speed, and the applied pressure in the vertical flat grinding on the surface roughness of silicon wafers using Taguchi orthogonal array design. Besides, the pits and resistivity on the wafers were studied as well. The experiment results showed that the diamond grain size and the wheel rotation speed of the vertical flat grinding for the roughness of wafers obtained are the relatively larger significant contribution. When the smaller diamond grit size, the faster wheel rotation speed, the faster table rotation speed, and the smaller applied pressure in the flat grinding are employed, the traces produced by the grains are denser and the chip thickness and the depth of cut were smaller, which cause the silicon wafer to produce the higher degree of the ductile grinding. This will lead the wafer surface to produce the smaller amount and size of the pits, thereby generating the lower surface roughness. In addition, the center site of the wafer obtained is the smaller amount and size of the pits than the outer of the wafer, which produces the better surface roughness and the lower resistivity.