For the milling process dynamic model set up on regenerative chatter theory, a new semi-analytical method for milling process stability prediction based on the improved Euler method was proposed. At first the state transition matrix was deduced by the improved Euler method, then the stability of milling process under specific cutting condition was determined with the Floquet theory, further more the stability lobe diagram (SLD) of milling process was obtained by changing spindle speed and axial cutting depth. Comparing with semi-discrete simulation results, found that the proposed semi-analytical method based on the improved Euler method has higher computation efficiency under ensuring prediction accuracy.