The effective extraction of radar echo signal is a key step in the process of Doppler signal processing in interior ballistics. Currently manual interception is usually adopted in the engineering application. The method often causes high error and low precision. Aiming at these problems, an effective method of Doppler signal automatic extraction is proposed. The obvious noise can be intercepted. According to the principle of Doppler, the method uses short-time Fourier transform (STFT) to acquire the velocity of the entire signal. The maximun velocity point is judged as the terminal point for the effective signal. The improved method of multiple-window energy ratio is adopted to determine the starting point. The experimental results through simulated signal and actual signal show that the average error of the method to extract the starting points and terminal points of the effective signal is 0.1875 μs.