A hydraulic control system is disclosed, which can minimize the flow rate of a hydraulic fluid being discharged from a variable displacement hydraulic pump by using pilot pressure constantly produced by a pilot pump when a switching valve is in a neutral position, and can adjust the flow rate of the hydraulic fluid being discharged from the variable displacement hydraulic pump by using pressure produced by a pressure generator positioned at the most downstream side of a bypass passage if a separate input signal is applied to the pressure generator when the switching valve is operated. The hydraulic control system includes a main variable displacement hydraulic pump, a pilot pump, a plurality of actuators, a switching valve interposed between the main pump and the actuators, a load pressure signal passage for guiding a part of the hydraulic fluid to a tank via the first flow control device, and a flow control device for the main pump installed on one side of the main pump to control the flow rate of the hydraulic fluid by adjusting the inclination angle of a swash plate in the main pump.