Cutting parameters including cutting speed, feed rate, depth of cut and the number of passes have significant influence on both machining quality and machining economics. Cutting parameter optimization involves optimal selection of a combination of these parameters. It is an essential part of a computer-aided manufacturing system. In this paper, an optimization model based on minimum production cost for multi-pass turning operations is developed. Various realistic machining conditions and machining requirements are incorporated in the model as constraints. Optimal solutions are found by a nonlinear programming solution approach. A turning example is presented to test the model. Compared with the literature and the cutting regimes recommended in machining data handbook, our model and solution method are simple and generate much lower unit production costs.