A 100J level KrF laser pumped by an intense relativistic electron beam –Flash II has been developed successfully. The main structure and specifications of the laser are reported in this paper. The maximum laser output energy of 157J with a parallel resonator at the diode voltage of 840kV and current of 200kA are obtained. The peak power is measured to be more than 2.0GW. The dependence of laser output energy with Kr and F2 concentration are also studied.