The impedances of PFN transmission line driven discharge XeCl laser were measured from 1 to 10 atmospheres total gas pressure. The experimental result shows that the increasing of total gas pressure oan improve the impodanoe matching between PFN and gas discharge and increase the energy deposited in gas discharge. On the other hand, the fluorescence duration of XeCl B→X transition is reduced by various quenching processes at high gas pressure. According to these two effects, the optimum total gas pressure for discharge XeCl laser is about 4~6 abmosplieres.