In order to studythe output characteristic of the excimer broadband pumped alkali laser (XPAL), the time-dependent rate equationisestablished forthe five-level XPAL, which takes Cs-Ar mixed gas as the gain medium.Using triangle pulse pump, the output laser energy curvesare obtained by simulation when pump pulseenergy, temperature, and concentration of relaxation gas change, and the slope efficiency obtained from the model agrees well with the experimental data.The results show that, the higher the temperature is, the higher the threshold and slope efficiency of the XPAL are, when the other conditionsare fixed;D2 line laser disappears when the concentration of relaxation gas is large enough;and XPAL has the highest efficiency when the temperature is around 515K.