For the laser system performance, the threshold condition is of great significant. The threshold condition of low gain broadband-pulsed excimer laser is closely relative to the pump pulse . Based on the rate equations of four-level laser energy systems, the analyticalmethods of gain switching and Q-switch are used to study the threshold condition of the low gain pulsed excimer laser. The threshold conditions in the different gain duration are given. The analytical results show the threshold condition of low gain excimer laser is fundamentally different from the cw laser in short gain pulse, and depends on time integrated gain coefficient that has to exceed a critical value.