A four-channel single-mode fiber optic rotary joint is designed, which is based on transmission theory of Dove prism. The optical signal coupling is implemented applying bevel gear. Furthermore, a scheme of the coupling adjusting is designed. The coupling loss is also analyzed, which is brought by the error between optical axis and rotary axis of Dove prism so that the installation precision of Dove prism is confirmed. Finally, the technical indicator of four-channel single-mode fiber optic rotary joint has achieved the level of congener foreign products. And this design can be expanded to eight-channel with primary configuration size by the enough optical aperture of Dove prism.