A dual frequency terahertz radar is designed based on the dual frequency terahertz gyrotron. The targets echo model including micro-Doppler information is established for the vibration, rotation and rolling targets. The simulation of micro-motion feature extraction is carried out by using the time-frequency analysis method. The simulation results show that the 0.11 THz radar and 0.22 THz radar have centimeter level detection ability for micro-motion feature extraction of vibration, rotation and roll. Under the condition of strong noise, the self-power spectrum time-frequency analysis can suppress the noise and improve the detection ability of micro-motion feature extraction. Through the cross-power spectrum time-frequency analysis of 0.11 THz and 0.22 THz radar echo baseband signals, the micromotion feature extraction of the same frequency is enhanced, and the noise is suppressed, which helps to extract micro-motion feature information.