The compton backscattering experiment is put forward to produce hard X rays of high-brightness and polarization for making up the shortcoming of no hard X-ray source in NSRL. And the hard X rays wevelength will be adjusted contiunally by tune the wavelength of FEL. The parameters of FIRFEL and the project of the compton backscattering experiment are present for the storage ring of NSRL, and the theorectical results are given also.