The Z-map models of workpiece and tool swept volume are established by an intersection algorithm between line and free-form surface, and then update of the workpiece is realized by a boolean operation between workpiece Z-map model and tool swept volume Z-map model. 利用直线与自由曲面的求交算法实现了工件曲面和刀具扫描体曲面Z-map模型的建立,将两个Z-map模型进行布尔运算完成了工件曲面Z-map模型的更新。