A new detection system for detecting terahertz (THz) wave radiation is described. The niobium nitride and aluminium are used to fabricate the bi-material micro-cantilever arrays. The role of the niobium nitride is to absorb THz wave radiation, and the aluminium is the deformation material. The bi-material of niobium nitride and aluminium has the characters of a large difference in thermal expansion coefficient and deformation after absorbing heat, so it can combine the technology of bi-material micro-cantilever arrays detecting infrared and realize the detection of THz wave. The micro-electromechanical system (MEMS) technology is adopted to fabricate the substrate-free bi-material micro-cantilever arrays. In order to prevent the heat diffusion, the micro-cantilever is placed in a vacuum chamber which has the function of vibration prevention, and the mechanical pump and molecular pump are used to keep the high vacuum for improving the signal-to-noise ratio of the detection system. The reflection-type visible light optical readout way is used to acquire the THz wave information indirectly. Furthermore, the method of difference processing is used to process image for improving resolution of the system.