In this paper, the parameter optimization problem for multi-pass turning operations is studied. A mathematical model based on the minimum production cost criterion is developed. The unwanted material is removed by one finishing pass and at least one roughing passes depending on the total depth of cut. Maximum and minimum allowable cutting speeds, feed rates and depths of cut, as well as tool life, surface roughness, cutting force and cutting power consumption are constraints of the model. Optimal values of machining parameters are found by three methods: integer programming, nonlinear programming, and genetic algorithms. An example is presented to illustrate the effectiveness of the optimization model and solution methods. The model generates lower unit production costs compared with the results from the literature and machining data handbook.