Tool bits with two-dimention chip breaking groove for turning stainless steel 1Cr18Ni9Ti are investigated, the formulas of limiting feed and depth of cut are obtained, the effects of tool cutting edge angle, chip breaking groove width, corner radius and cutting speed on chip breaking region are analyzed, and the chip breaking discriminant is established. This discriminant may be used to forecast the possiblity of the breaking of chips of tool bits with two-dimention groove or to select the suitable tool bit in turning stainless steels according to a given regime of machining.