In the terahertz confocal scanning imaging, the imaging quality is to be improved for the reason that terahertz laser can not output the beam constantly and that the signal collected is weak, and so on. The comparison among median filtering, block-matching and three dimensional (3D) filtering (BM3D), non-local means filtering (NLM) and median non-local means filtering (MNLM) is made after eliminating the background suppression resulting from laser shaking. The influence of the filtering parameters on the processed effect is studied. The results of image processing show that on the condition of applying definitive filter parameters to the investigation images, MNLM′s effect is better than that of NLM′s, and NLM′s effect is better than BM3D′s, while median filtering′s effect is the worst.