The study of power output from free electron lasers (FEL) has shown that to gain higher output power the FEL at infrared region is better than those at the ultraviolet. Superradiation generation, operational conditions have been obtained in which the pulse width of the relativistic electron beam and the transmission of resonator eavity were studied The effectof energv divergency of the relativistic electron beam △r0/r0 on the energy conversion ef flcieney hasalso been discussed.