The invention relates to a rotary Raman laser radar system based on a grating technology light splitting structure, which comprises a laser emitting system, a receiving system, a light splitting system, a photoelectric detection system and an information processing system, wherein the light splitting system comprises a positive lens, a blaze grating, an optical fiber array, optical fiber couplers and an optical fiber Bragg grating, the optical fiber array and the blaze grating are respectively positioned at the front side and the rear side of the positive lens, a plurality of optical fibers are connected to the optical fiber array, the optical fiber coupler is arranged on each optical fiber and provided with three ports which are respectively PA, PB and PC, and the port PB is connected with the optical fiber Bragg grating. According to the invention, regulation freedom of the rotary Raman laser radar system is reduced; and the rotary Raman laser radar system has the advantages of compact structure, small volume and light weight, and has a certain daytime remote sensing detecting capacity so as to be suitable for vehicle-mounted, air-mounted and satellite-mounted application.