The reason of residual voltage of storage capacitor in laser pumping system is analyzed. After long-term experiments and research，the occurring reason and increasing regularity of residual voltage are given. Furthermore，considering the increasing regularity of residual voltage with the practical application of laser equipment，the actual tolerance of residual voltage in practice are given，and maintenance decision-making principles of laser equipment are defined. It is pointed that increasing the voltage of storage capacitor is useless and detrimental to the working life of laser equipment in maintaining，according to the increasing regularity of residual voltage and the working characteristics of pumped xenon lamp.