To improve the machining process and productivity,an optimization method by virtual machining to acquire the machining parameters in turning is presented so that the optimization of machining process can be realized by optimizing the machining parameters in NC programs.The algorithm to acquire the implicit cutting depth and cutting speed based on the profile polygon representation of workpiece is highlighted during virtual machining,and the optimum cutting parameters can be searched with optimization algorithm,and then an optimized machining process is achieved via revising the spindle speed and feed rate in NC a program.The results of controlled actual cutting experiments show that the machining time is reduced significantly and the maximum power of the machine tool is reached.The machining process and productivity are improved with optimization.