Magnesium alloy is one type of metals that is currently widely used to replace various components in the biomedical field, but because of its low melting point. special attention is required during the machining process of magnesium alloy. This study aims to optimize machining parameters specifically cutting speed, feed rate and rotary tool speed. Analyze was done by using Response Surface Method of Box Behnken Design. The rotary turning of magnesium AZ31 was done to achieve minimum wear value on the cutting tool. The use of pressurized cold air was also applied to this study to reduce the  temperature between work piece and rotary cutting tool. Based on the analysis using Response Surface Method of Box Behnken Design obtained,  the optimum value for the minimum tool wear in the amount of 0,27728 mm at cutting speed of 80 m/min, feeding speed of 0,1 mm/rev and rotary tool speed of 45,7071 rotation/min. The mathematical modeling obtanied is Vb = 0.3550 + 0.000797 Vc + 0.3950 f - 0.008159 Vt + 0.000090 Vt*Vt.