Abstract: A NC lathe was made by NC transforming with an old ordinary lathe.With ordinary PC as the host for micro-computer NC system, using pulse width-modulating circuit and smooth division circuit for the driving power supply of step motor, and a rebuilt old ordinary lathe added with signal-receiving 4 station electric tool post as the lathe body itself, people have realized multi-functions, low-cost and automation for the lathe, the precision and efficiency of the lathe was increased.