The invention discloses a novel method for extracting a radar target micro-motion cycle in a self-adaptive mode. According to the method, only radar is utilized for receiving target echo data to estimate a micro-motion cycle of a detected motion target, and a contour extraction and curve fitting method for a time frequency diagram of the radar target echo data is utilized for accurately estimating the target micro-motion cycle. Signal time frequency distribution is obtained based on the target echo data received by the radar through the short-time Fourier transform, then the short-time Fourier transform is carried out on the obtained time frequency distribution curve, a time frequency changing contour is extracted through the method of setting a threshold value in a self-adaptive mode, then a polynomial fitting method is adopted for carrying out detail smoothness on the obtained rough contour, and finally the target micro-motion cycle is estimated by carrying out spectral peak detection on the smoothed oscillogram. The novel method for extracting the radar target micro-motion cycle is low in cost, self-adaptive, steady and high in precision.