The invention relates to a control system for performance compensation of construction machinery. According to an embodiment of the invention, when the fuel feeding is reduced as fuel of a mechanical engine is exposed, or engine output is decreasing as the open value of a throttle value is insufficient compared with a normal condition, hydraulic pump control instructions for controlling pump torque of a hydraulic pump are reduced, so that the engine rotation number is prevented from being decreased too much, and the pump torque can be maintained well.