In order to improve the processing efficiency of automotive covering molds，the torus cutters are usedIn the process of semi-finishing and finishing of small curvature surface. Through the tool contact geometric analysisof 3-aixs machining smal-curvature surface，it determines that the optimal cutter feed direction is alone the directionof the workpiece height changing

which can maximize effective cutting interval. Based on the conclusion，tool pathplanning is done for two kinds of special surface. Vertical section method is used for the single-direction-curvaturechanging surface，and the section is along the direction of maximum principal curvature. The experiment shows thatthe vertical section method can improve the machining efficiency by 25 %，compared with the contour methodgood surface quality issimulation result showsthree-dimensional offsetgenerated. Radiation finish machining methodis adopted on the round-drum surfacethat this methodmethod，and cancanimprove the machining efficiency by 22.64%，compared withandthetheavoid the surroundingowe cut.