To provide a priority to a specified cylinder or motor, when two hydraulic valves are simultaneously opened.

A hydraulic system 10 for a construction machine is provided with a pump 12 supplying a pressurized fluid from a fluid storage tank 14 to at least the first and second main valves 26, 27. The first and second input devices 46, 47 generating the first and second control signals expressing a required actuation of the hydraulic system are included in the system. A controller 44 responding to at least the first and second control signals is provided and a correction signal is generated in response to the first and second control signals. The second main valve is actuated in response to both second control signal and correction signal.