The classical Preston equation considers that the material removal is linearly related to time, velocity, and pressure. However, in the wheel polishing technology, it is found through experiments that there is a nonlinear relationship between the rotational speed of the polishing wheel and the amount of material removed. In order to accurately control the material removal in the polishing wheel variable speed machining strategy, it is necessary to modify the classical Preston equation. In this paper, the control variable method is used to carry out the sampling experiment: the time and pressure are set as fixed values, and the polishing wheel speed is set as a variable and the value is between 0-4rps. Then the data points were analyzed and a least squares fit was used to obtain a non-linear function between the rotational speed of the polishing wheel and the amount of material removed. Finally, the classical Preston equation is modified to obtain the removal equation suitable for the variable speed machining strategy. © 2023 SPIE.