Abstract: The finish turning experiment of AZ91D magnesium alloy was carried out at different cutting speeds, and the breaking performance and shape of chips and surface quality of workpiecr at different process parameters were compared. The results show that, at the premise of constant cutting depth, with the increase of cutting speed and the decrease of feed, chip deformation decreased, chips shape changed from C shearing to strip, the breaking performance of chips and the surface quality of the workpiece all were poor grandually. Powder-like chips formed and accumulated in chip groove at the cutting depth of 0.06 mm, and thus to easily cause magnesium alloy combusting. The better cutting process parameters as follows: vc=107.388 m·min-1, f=0.09 mm·r-1, ap=0.1 mm, and the workpiece cutted at above parameters met the design requirements.