Terahertz(THz) time domain spectroscopy includes abundant information about the sample,so the image for the structure of the sample can be reconstructed. How to resolve some sample parameters and reconstruct image using phase information and amplitude information of THz wave is investigated. A comparison between phase imaging and amplitude imaging is carried out. The results show: the quality of phase imaging is better than the quality of amplitude imaging if the absorbing of the sample is small;the excursion of the peak brings some effect on phase imaging. The splitting phenomenon of output spectroscopy is found in the experiments,namely THz time domain spectroscopy changes from one peak to two peaks. The analysis shows that this phenomenon results from abrupt change of the thickness or refractive index. This phenomenon can be used to study outline imaging in Thz field.