Abstract: The broadening of excimer laser pulses during amplification was analysed. To attain a shorter laser pulse, a compressing technique called pulse negative feedback was developed with the gain saturation switch applied to the amplification in an discharge pumping excimer laser.Combined with the echelon-free induced spatial incoherence technique, it can output shorter pulses with the beam uniformity maintained. A 100 mJ, 10 ns laser pulse was achieved in the LPX-150 excimer laser which acts as the laser source of the “heaven-Ⅰ” system. The spatial uniformity of the pulse remained within 3%.