Automatic-switch type load sensing hydraulic system

The invention provides an automatic-switch type load sensing hydraulic system and belongs to the field of marine crane hydraulic systems. The system comprises a load sensing variable pump module, a first electro-hydraulic proportional valve module, a second electro-hydraulic proportional valve module, a first actuating mechanism, a second actuating mechanism and a series switching valve module, wherein the first electro-hydraulic proportional valve module and the second electro-hydraulic proportional valve module are respectively connected with the first actuating mechanism and the second actuating mechanism; the load sensing variable pump module comprises a variable pump and a load sensing valve which are connected to each other; the first electro-hydraulic proportional valve module comprises a first proportional directional control valve; the second electro-hydraulic proportional valve module comprises a second proportional directional control valve; and the first electro-hydraulic proportional valve module and the second electro-hydraulic proportional valve module are connected is series through the series switching valve module and share the load sensing variable pump module, and a T oil-return port of the first proportional directional control valve and a P oil-inlet port of the second proportional directional control valve are in communication. By the aid of the series switching valve module, all actuating mechanisms operate at the same time, and the maximum oil amount of the variable pump is shared.