Superconducting accelerator, which uses SRF cavity working at cryogenic environment, can operate in macro-pulse or CW modes. Due to its large beam aperture, the interaction between beam and cavity can be reduced remarkably. After the development of more than a half century, SRF technology is quite advanced and has been applied in different kinds of light sources. In this paper, basic principle of SRF, fabrication of elliptical SRF cavity and structure of typical cryomodule of SRF accelerator are introduced.