The invention discloses a terahertz compressive imaging system and method. The system comprises 1, a terahertz generation and detection unit which comprises a laser source, a terahertz emitter and a terahertz detector, 2, a terahertz wave coding measurement unit which comprises a light splitter lens, a semiconductor mask plate and a digital projection device, wherein the digital projection device produces encoded pattern light beams, the light beams act on the semiconductor mask plate to cause semiconductor carrier distribution and the semiconductor mask plate allows the specific terahertz wave to go through the mask plate and keeps congruity of the specific terahertz wave and the light beam pattern so that terahertz wave spatial modulation is realized and a semiconductor mask plate coding function is realized, and 3, a terahertz reconstruction imaging unit which is used for recovering the original image through a reconstruction algorithm so that terahertz imaging is realized. Through combination of digital light processing projection and semiconductor photo-induced carrier characteristics, terahertz wave light-controlled modulation is realized. The system has the advantages of complete digitization, fast rate, high programmable capability, low cost and integration easiness.