Positive flow and negative flow universal hydraulic system of excavator

The invention discloses a positive flow and negative flow universal hydraulic system of an excavator, and belongs to the field of engineering machinery. According to the technical scheme, the positive flow and negative flow universal hydraulic system of the excavator is characterized by comprising a pilot control device, a main valve assembly, an execution mechanism and a flow pump assembly. The main valve assembly comprises at least one valve body, wherein a central bypass oil duct and an oil return duct are arranged in the valve body. The flow pump assembly is connected with the main valve assembly. The main valve assembly is connected with the execution mechanism. The pilot control device controls the execution mechanism to move through the main valve assembly. A modular connecting oil duct is arranged on the valve body, communicated with the central bypass oil duct and the oil return duct and provided with an outer connecting port, and the outer connecting port is provided with a screw plug or a negative flow feedback valve. Through interchange of the screw plug and the negative flow feedback valve of the main valve assembly, conversion between a positive flow hydraulic system and a negative flow hydraulic system of the excavator is realized, and the production cost and management difficulty are lowered for manufacturers.