The present invention relates to methods of controlling the current of a flash lamp, particularly, it relates to methods of controlling the current of a flash lamp in which during periods of time between main discharge pulses the flash lamp is simmered thus extending the flash lamp's service life and stabilizing its gas discharge channel, and can be used for driving pump lamps of pulsed lasers. The method comprises delivering of main current pulses to the flash lamp that cause an intense gas discharge. During the major part of time interval between adjacent main current pulses a strength of the simmer current is maintained at a first strength level, which is as low as possible while still ensures an existence of the discharge channel, whereas prior to delivering each of said main current pulses, the simmer current is increased to a second strength level and is selected to be equal to a lowest possible current strength level that is sufficient to ensure that the tube of said flash lamp is entirely and uniformly filled with plasma. In another embodiment, prior to delivering each of the main current pulses, the simmer current is being increased until resistance of the flash lamp becomes equal to the value with which the main discharge phase begins with a monotonic voltage growth.