In this paper, terahertz photoinduced force microscopy (THz PiFM) is designed and built, which realizes the near-field photoinduced force nanoscopic imaging measurement in the terahertz band for the first time. Based on the atomic force microscopy, the system uses the sensitive detection ability of the probe to the force, and realizes the terahertz near-field microscopic imaging without detector. The system detected the light field gradient force generated by the near-field dipole interaction between the probe and the sample. The near-field nanoscopic imaging characterization of monolayer MoS₂ grains excited by visible light was carried out, and the mechanism of near-field optical signal enhancement at the grain edge was analyzed. The results show that THz PiFM has a highly sensitive detection capability for carriers in two-dimensional materials. Compared with the traditional terahertz near-field microscopy imaging technology, THz PiFM does not require terahertz detector, and is a new low-cost, high-performance terahertz near-field microscopy imaging technology, and can achieve superior spatial resolution and imaging signal-to-noise ratio.