A method based on quasi-static and Multi-level Fast Multi-pole Algorithm (MLFMA) is introduced to compute the micro-Doppler echo by motion body targeting with arbitrary shape. The joint time frequency analysis algorithm is used to calculate some typical motion's micro-Doppler echo. Furthermore, efforts were made to extract the instantaneous frequency and then compare it with the point target's instantaneous frequency in accord with the same micro-motion. The results indicate that they share the same trend and the current method is efficient.