A six-beam multiplexing master-oscillator-power-amplifier (MOPA) high power KrF excimer laser system has been built at CIAE for fundamental research on laser–plasma interaction. The MOPA system consists of front-end, two-stage KrF amplifiers (preamplifier and main amplifier) pumped by two-side electron beams, an optical angular multiplexing system, a synchronization trigger system, and a controlling-data acquisition system and some diagnostic systems. The total energy of the six-beam output from main amplifier on the target is 100 J/23 ns, the divergence of one beam is 0.2 mrad, the focal spot diameter is 220 μm, and the focal intensity on the target is 1013 W/cm2.