The prototype of ZCS-SRC (zero current switching-series resonant converter) switching mode power supply for high-power lasers is developed successfully based on a novel resonant technique. Compared with the conventional and PWM hard-switching power supplies, the outstanding technical indexes of the ZCS-SRC which holds a leading position in China are as follows: operating frequency is 50 kHz, efficiency is 82%, output current is 0～80 mA, and the fluctuation of current is ≤±1 mA. The power supply for the high-power gas laser provides a steady discharge current without the need of any amperites. The discharge current can be adjusted from zero and is independent on gas density and gas pressure.