In plunge grinding processes of workpiece with varying radius of curvature, the radius ratio and speed ratio vary continuously during one revolution of workpiece. The plunge grinding process is investigated with a computer simulation method. Main conclusions obtained are as follow: (1) Under constant rotation ratio, both radius ratio and speed ratio become maximum at the same angle at which the second derivative of profile function becomes maximum. (2) Under constant rotation ratio, normal grinding force and surface roughness become larger in a position with higher speed ratio. (3) Under constant speed ratio, normal grinding force and surface roughness distribute almost constantly on the circumference of workpiece, but the variation ratio of residual stock and wheel wear rate become larger because of higher effect of radius ratio as compared with that under constant rotation ratio.