Abstract: In order to achieve high quality and high brightness electron beam,a photocathode injector is used as the electron source in the experimental setup of a free electron laser (FEL).The drive laser system is a master oscillator power amplifier configuration,consisting of a confinuous wave diode-pumped mode-locked oscillator,one double-pass and two single-pass regenerative diode-pumped pulse amplifiers and a four fold frequency conversion part.After adjustment,single micropulse energy of 4μJ with less than 3 percent of jitter at wavelength 266nm was obtained.These micropulses were contained within a macropulse envelope as long as 2μs to 6μs.In the experiments,adopting C2Te photocathode as the photoinjector,more than 40A electron beam was obtained,meeting the requirement of beam current for the FEL.