A method for actuating a hydraulic system of a transmission comprising a variable displacement hydraulic pump and a pilot-controllable system pressure valve, the method including, in order to determine a pump characteristic curve of the hydraulic pump, initially transferring the hydraulic system into a defined operating condition range in which the volumetric output flow, routed via the system pressure valve and applied at the system pressure valve by the hydraulic pump, is greater or less than a hydraulic fluid flow out of the hydraulic system. The method further includes pilot-controlling the system pressure valve to set a defined pressure level of the system pressure. The method additionally includes reducing or increasing the volumetric output flow while monitoring the system pressure, and determining a volumetric output flow corresponding to the hydraulic fluid flow of the hydraulic system with a certain deviation of a current system pressure from the defined system pressure.