It is noteworthy that terahertz time-domain spectroscopy (THz-TDS) has been pioneered as a spectral measurement tool, which has drawn much attention in the field of terahertz (THz) wave. Conventional THz-TDS systems employ a stepped delay line for their optical delay line scan and utilize lock-in amplifier (LIA) for the acquisition of THz signals. In this approach, the speed of THz signals sampling is too slow to be introduced into some applications which require a high-speed performance. And the THz waveforms can be acquired in rapid scan THz-TDS system. Therefore, numerous practical applications for THz-TDS systems can be entered much more easily. In this review, we describe the technique for rapid scan THz-TDS and illustrate the various implementations of the technique with recent domestic and oversea examples. In addition, an improved method for rapid scan is proposed.