Magneto-optical materials are the indispensable and key functional materials in the field of modern optical communication. For the miniaturization of devices, high quality magneto-optical thin films have attracted much attention. The sillenite type Bi25FeO40 has a cubic crystal structure with high symmetry. The concentration of bismuth ions per unit volume is high, so it should have a strong magneto-optical effect in theory. However, its application is restricted due to low magnetism and difficulty in preparation. In this paper, Bi26-x-yMxNyO40 (M, N=Fe, Co, Gd) magneto-optical thin films with cubic sillenite type were deposited on yttrium-doped zirconium dioxide (YSZ) substrate by the magnetron sputtering method. Their morphology, magnetic properties, transmittance, and magnetic circle dichroism were discussed. Smooth surface morphology of the films was observed by atom force microscope. The thickness of the films is about 190 nm. The valence states of bismuth, iron and cobalt in the films are all +3, and other valence states are not observed, so they are meeting the charge balance. The transmittance in the near infrared region is about 60% to 70%. At room temperature, the films show superparamagnetic effect, and the magnetic properties gradually increase with the increase of doping ion concentration. And the saturation magnetization of Bi13.6Gd2.7Co4.0Fe5.7O40/YSZ film reaches 29 emu/cm3. The Bi13.6Gd2.7Co4.0Fe5.7O40/YSZ film exhibits a strong magneto-optical effect, the magnetic circular dichroic spectrum signal is up to 1 710 deg/cm at wavelength of 716 nm. Therefore, Bi13.6Gd2.7Co4.0Fe5.7O40/YSZ film is expected to be used in integrated optical isolators and other optical communication devices.