Disclosed is a method for controlling the flow rate of a hydraulic pump in order to reduce the discharge flow rate of the hydraulic pump when the upper rotating body of an excavator rotates rapidly. The present invention relates to a method for controlling the flow rate of a hydraulic pump, and provides a method for controlling the flow rate of a hydraulic pump of a construction machine, comprising: a step of detecting the operation amount of a rotation operation lever, and the rotation pressure generated in a swing motor; a step of calculating the flow rate required for rotating, the flow rate corresponding to the operation amount of the rotation operation lever; a step of calculating a rotation acceleration first inclination value for increasing the discharge flow rate of the hydraulic pump to a certain inclination value from a rotation initiation time when the upper rotating body rotates; a step of calculating a second inclination value compensating for the first inclination value by a difference value between the detected rotation pressure value of the swing motor and the reference pressure corresponding to the set pressure of the relief valve of the swing motor; and a step of restricting the discharge flow rate of the hydraulic pump such that the increased amount of the flow rate required for rotating is restricted to the flow rate of the second inclination value.