In a controller (229) of a hydraulic control system in a construction machine, a valve control signal calculating function (301), when an operation pattern signal (A-1) of an actuator (201, 202...) is outputted, selects an output pattern from a plurality of output patterns of auxiliary valve control pressure stored in association with the operation pattern signal as a function of a signal of the difference between a discharge pressure of a pump and a maximum load pressure, calculates an auxiliary valve control pressure (Pc) corresponding to the differential signal based on this output pattern, selects a set of corresponding changing speeds (K...K...) from a plurality of sets of changing speeds of auxiliary valve control pressures stored in association with the operation pattern signal, and calculates valve control signals (S21-S26) by combining these auxiliary valve control pressures and changing speeds. A pump control signal calculating function (300), when the operation pattern signal (A-1) is outputted, selects corresponding sets of control gains (LSD, LSU) and of target differential pressures from a plurality of sets of control gains (LSD, LSU) and a plurality of sets of target differential pressures stored in association with the operation pattern signal (A-1), determines a deviation between a differential signal and its target differential pressure, and calculates pump control signals (S11, S12) for decreasing this deviation of differential pressure by use of this deviation of the differential pressure and the selected set of control gains (LSD, LSU), to thereby control a displacement of the hydraulic pump (220).