In this article the problem of simulation of milling process for complex surfaces with the estimation of one of its main characteristic, Material Removal Rate, is solved. A simulation runs with the offered algorithm which presents the workpiece cuts as regions, that allows to execute simulation of machining with using of “crossing” and “difference” operations above the plurals of polygons on a plane. The “crossing” operation allows to define the area of material which is removing by tool from the cut on some step, and a “difference” operation reproduces new geometrical shape of the cut of the workpiece after material removing. Simulation results are used for stabilizing of cutting process in the NC program which is created by one of the CAM systems.