A pulsed power supply has been developed for exciting a copper vapor laser with a bore diameter of 80 mm and a discharge length of 2890 mm. The pulsed power supply has two thyratrons, an LC‐inversion circuit and a two‐staged magnetic pulse compression circuit. An efficiency of 82% has been obtained which is defined as the ratio of energy stored in the storage capacitor to the output energy of the magnetic pulse compression circuit, with a voltage greater than 40 kV, averaged output power of 24 kW, and voltage rise time of 70 ns. The pulsed power supply was successfully operated for more than 2000 h and an optical output power of 272 W was obtained.