The present invention relates to a device and a method for controlling a hydraulic pump in a construction machine. The method for controlling a hydraulic pump in a construction machine comprises: an engine dynamic characteristic change checking step (S20) for checking whether an engine dynamic characteristic deviates from a predetermined permissible range when pump torque, required by a hydraulic pump, is reached by applying a load to the hydraulic pump; a pump load applying step (S40) for applying a pump load to the hydraulic pump, so as to increase the pump torque up to a specific torque with a specific slope, when the engine dynamic characteristic exceeds the predetermined permissible range in the engine dynamic characteristic change checking step (S20); an information collecting step (S50) for collecting information, generated at the time of applying the pump load, including information about the engine RPM, information about the angle of a swash plate of the pump and information about the pressure of discharged working oil in the pump load applying step (S40); a map data generating step (S60) for generating a new torque slope map (220a), by generating a torque slope per load section, on the basis of the information collected in the information collecting step (S50); and an updating step (S80) for updating the existing torque slope map (220) to the new torque slope map (220a) generated in the map data generating step (S60), wherein the hydraulic pump is controlled by the new torque slope map (220a) updated in the updating step (S80).