In micro cutting process, cutting forces affect greatly the tool life and the machining precision. Therefore,it is very significant to study the variations of cutting forces and the factors affecting the forces for determing the machining parameters and for improving the performance of machining systems. In this paper,the theoretical formulas and mathematical model of the micro cutting are established to calculate the cutting forces by using the axi symmetric theorem and by considering effects of the rounded edge radius of a cutting tool.The effects of cutting parameters,tool materials and workpiece materials on the cutting forces are analyzed,and the experiments are coincident with the theoretieal analysis well. The results show that,when the cutting depth ap,amount of feed f and the cutting speed v range in 0.002-0.032 mm,0.01-0.20 mm/r and 20-120 m/min,respectively,the forces Fz and Fy change in 100-1030 N and 40-700 N. Also,decreasing the rounded edge radius will reduce the contact length between the tool flank surface and the workpiece and the deformation of the workpiece materials below the cutting edge so that the quality of the machined surface is improved. Furthermore,the effect of cutting speed on the cutting force can be reduced by controlling the ratio of the cutting depth to the rounded edge radius,and the ratio of Fz/Fy can be controlled by adjusting the ratios of the feed per revolution and cutting depth to the rounded edge radii.