Based on accurate measurements of voltage and current between electrodes of a fast discharge XeCl laser, together with computer analyses, the kinetic impedance of gaseous mixture at high pressure of 3 to 8 atmospheres under discharge was obtained. The high impedance droped down to a fraction of ohm within several nanoseconds. The discharge peak currents and corresponding impedances of laser cavity at various charge voltages and gas pressures were studied. The results show that it is impractical and unimportant to match precisely the impedances of discharge plasma and of transmission line.