How to plan the tool path and obtain high-quality CNC(computer numerical control) code is one of the key techniques for machining the toric surface with slow tool servo technology. A tool path planning method based on equidistant surfaces was proposed. The surface equations of the toric surface and its equidistant surface equations were derived. Two kinds of guiding curves and two discrete methods were compared and analyzed. Optimized scheme of the tool path planning was selected. The NC code generation software for machining toric surface with the slow tool servo technology was developed by using VB.net language. The generated NC code was verified based on the Vericut CNC machining simulation platform. The residual area of the virtual machined surface relative to the theoretical surface was intuitively shown. Simulation results show that the tool path planning method based on equidistant surfaces is feasible. The results show that by changing the non-primary term of the toric surface equation from a to a+r_d, its equidistant surface equation can be obtained. The tool path planning method based on equidistant surfaces is suitable for machining convex-toric surface using slow tool servo technology. The proposed method has some reference values for processing optical elements having other surface shapes by slow tool servo technology.