Terahertz radar has extremely high resolution when measuring single targets. However, under multi-target conditions, the use of classical chirp waveform modulation may result in false difference frequency combinations, thus creating ghost targets. Aiming at this problem, a design scheme of multi-target detection for terahertz radar with improved waveform working at 0.22 THz is proposed. It consists of two parts:trapezoidal wave and triangular wave. The speed-distance blur range is calculated by the upper and lower sweep of the trapezoidal wave, and the relative speed of the target is detected by the constant frequency band. Nevertheless, the ghost target still exists owing to the mismatch of the velocity-distance intersection. The subsequent triangular waves with different frequency modulation slopes can help completely eliminate the ghost target. The architecture of the terahertz radar system is given in this paper, and through the near-realistic simulation, it is proved that the accuracy of terahertz radar for difference frequency pairing will be greatly improved under this new waveform system.