The invention discloses a magneto-optical modulator based on a photonic crystal cross waveguide. The magneto-optical modulator comprises the photonic crystal cross waveguide with a TE forbidden band. The modulator further comprises one input end (1), three output ends (2, 3 and 4), background silicon dielectric cylinders (5), isosceles right triangle defect dielectric cylinders (6), a defect dielectric cylinder (7), an electromagnet (8) providing a bias magnetic field, a modulation current source (10) and a modulation signal (11); the left end of the photonic crystal cross waveguide is the input end (1), the output ends (2, 3 and 4) are located at the lower end, the right end and the upper end of the photonic crystal cross waveguide respectively, the defect dielectric cylinder (7) is located in the center intersection position of the cross waveguide, and the four isosceles right triangle defect dielectric cylinders (6) are located at the four intersecting corners of the cross waveguide respectively; TE carrier wave light is input through the port (1) of the photonic crystal cross waveguide, and amplitude modulation light is output through any one of the ports (2, 3 and 4). The TE carrier wave light signal modulator is efficiently obtained.