The invention discloses a Fourier phase grating terahertz wave beam splitter. The splitter comprises a two-dimensional Fourier phase grid, a support frame, a rotating table, a disc, a base, a height adjusting knob and a rotating shaft, the four corners of the two-dimensional Fourier phase grid are fixed to the support frame through screws, the lower end of the support frame is fixed to the rotating table through position pins, the rotating table is fixed to the upper end of the disc through a height adjusting knob and a height adjusting insertion hole, and the disc is fixed to the upper end ofthe base through a metal column and a fixing hole. The upper end of the rotating shaft sequentially penetrates through the through hole in the middle of the disc and the through hole in the middle ofthe rotating table to match the round hole in the middle of the lower end of the supporting frame. On the premise that high diffraction efficiency is guaranteed, the beam splitter is simple in structure, the angle and the height can be adjusted, and the complexity and the cost of a system suitable for the beam splitter are reduced.