Abstract: Directional-control-valves is one of the key components in the hydraulic system of construction machines. The development course of directional-control-valves is summarized and the developing backgrounds and main defects are analyzed. It is especially discussed that newly existed load-sensing compensation technology, negative control and electrohydraulic proportional directional control valves with electrohydraulic load sensing and separate controlling of meter-in and meter-out orifices. At last, the future trends of this field are presented.

Key words: Directional control valves, Electrohydraulic proportional technology, Load-compensation, Load-sensing, Separate control of meter-in and meter-out