In angular multiplexing excimer laser system, studies on energy amplification of a train of laser pulses are crucial to determine beam number for reducing optical complexity, while strict requirements on alignment are needed for experiments. Based on principles of displacement and angular drift adjusted by near field and far field respectively, an optical automatic alignment system is designed, and corresponding computer software for closed-loop feedback controll is compiled. High adjustment accuracy with allignment errors of 21 μm in near field and 1.3″ in far field is obtained by using He-Ne laser. This system is applied to two pulse amplification experiment and works effctively.