In order to achieve the truncated amplified spontaneous emission pulse, the method of timeshare quenching was proposed in this paper. When the original pulse of the amplified spontaneous emission is 16.72 ns, the obtained best results show that the pulse width is truncated to 2.48 ns, and the shortening ratio is approximately 6.7. By analyzing the 12 acquisition results of the continuous amplified spontaneous emission truncation, 2.59 ± 0.05 ns amplified spontaneous emission pulse was obtained. The experimental results showed that the stability of the truncated pulse width is well. This method is applicable to truncate the ASE pulse in KrF excimer laser. It is significantly to the research of the inertial confinement fusion.