Abstract: Using a laser created plasma switch, a 1.58 ns short output pulse from a UV-preionized XeCl excimer laser is obtained. The influence of the beam energy intensity focused on the film surface for the generated plasma density is analyzed. The pulse shorting effects of different plasma density and hold time are discussed, and the experimental results are presented with the resonant cavity operating in stable cavity and unstable cavity modes separately. Working in stable cavity mode, the pulse width can be narrowed to 2.87 ns. While in an unstable cavity mode, by reducing the focused beam area to improve the energy intensity, a 1.58 ns short output pulse is obtained. This technique can applied to any other excimer laser.