Quantitative and variable hydraulic system of loading machine

The invention relates to a quantitative and variable hydraulic system of a loading machine. The shortcomings that a quantitative hydraulic system in an existing loading machine hydraulic system is high in energy consumption, and a variable hydraulic system in the existing loading machine hydraulic system is high in cost are overcome. The quantitative and variable hydraulic system is characterized in that a load sensing steering gear and a load sensitive flow amplification valve are connected to control a steering oil cylinder; a pilot valve and a load sensitive distribution valve are connected to control a working oil cylinder; an oil outlet of a load sensitive variable pump passes through a pressure-gradient control valve to be respectively communicated with an opening P of the load sensitive flow amplification valve and an opening P of the load sensitive distribution valve, a metering pump passes through an unloading valve to be communicated with the opening P of the load sensitive distribution valve, an opening LS of the unloading valve obtains a pilot oil pressure signal from the pilot valve, and an opening LS of the load sensing steering gear and an opening LS of the pressure-gradient control valve are communicated to provide a loading pressure signal for the load sensitive variable pump through a shuttle valve with the load sensitive distribution valve. By means of the quantitative and variable hydraulic system, overflowing losses, medium-position opening losses and high-pressure unloading losses are avoided, the energy consumption and the cooling power are low, and the oil liquid service life is long.