The grinding for cylindrical cam’s groove means grinding for groove’s flanks. For cylindrical cam with translating cylindrical followers, an auto-programming system for NC machining of cylindrical cam’s groove is developed. It can be applied to machine cylindrical cam with different types of curve grooves, by using cutter or wheel with different diameter. For validating geometry precision of the auto-programming system, emulation is carried out using the VERICUT, which is a NC machining emulator system. It is showed by the results of the emulation, there is excess of geometry error at bottom of groove when following situations are met: big pressure angle, high precision requirement and big diameter difference between wheel and roller. An important origin of such excess is computational error introduced by the auto-programming system in calculating the coordinates of wheel center.