The method of image processing of terahertz time-domain spectral imaging in the time-domain and frequency-domain is discussed. Compared to other intensity imaging, terahertz time-domain spectral imaging technology has an obvious advantage that it has a large amount of information. According to different requirements, different image characteristics are demonstrated by selecting different physical parameters in order to provide more accurate sample information. Each pixel corresponds to a time-domain waveform so that any amplitude or phase data point from the time-domain signal or its Fourier transform spectrum can be used to make graphs to remodel the space density distribution, the refractive index and the thickness distribution of samples. It is worth mentioning that, in the frequency-domain model, graphs can be made by different parameters at each frequency, such as amplitude, absorption, refractive index, energy, power and so on, which can be used to investigate the terahertz multi-spectral imaging technology. The results of these researches have important significance to improve the resolution of THz imaging and THz image recognition technology.