For the problem of chaff micro-motion on echo signal modulation, a single chaff echo construction method is proposed. Firstly the kinematic equation of a typical micro-motion mode of single chaff is established. Then, the single chaff echo in the micro-motion mode is simulated based on the scattering center, and finally the law of the micro-motion change of the chaff echo signal is analyzed by the time-frequency method. The simulation results show that the single chaff micro-motion model established in this paper can effectively reflect the micro-motion characteristics of the chaff echo signal, provide technical support for accurate establishing of the chaff cloud echo model, and provide theoretical basis for effectiveness of chaff jamming recognition and improvement of radar performance.