Cutting characteristics such as heat affected zone (HAZ), top and bottom kerf widths, ratio of top kerf width to bottom kerf width, and dross height are so reliant on process condition in the laser cutting of polymer materials. In the present research, a 60 (W) continuous wave CO 2 laser cutting machine was used for cutting the extruded samples of Polystyrene sheet with the thickness of 3 mm. The experiments were designed based on the statistical method, design of experiments. Three variables considered as process parameters including laser power (in three level of 60, 70 and 80 W), cutting velocity (in three level of 6, 10, 14 mm/s) and cutting with covering gas or without gas. The results indicated that the maximum feasible laser power and increasing cutting velocity using compressed air resulted in decreasing HAZ width. By gradual increase of the laser power the cutting mechanism converts from melting to evaporation. Increasing laser power and cutting velocity individually made the dross height smaller. The process parameters were optimized to achieve minimum top kerf width, minimum HAZ width, and ratio equal to 1.