The invention provides a hydraulic system based on a negative flow control system. On the basis of an existing negative flow control system, a flow regulation and control pressure reducing valve (9),a selection valve II and a selection valve I are additionally arranged. When a newly added functional valve set is in use, an original functional valve set is turned off through the selection valve IIand the selection valve I, and the newly added functional valve set communicates with a flow control valve (5) and the flow regulation and control pressure reducing valve. The flow of the newly addedfunctional valve set is regulated and controlled through the flow regulation and control pressure reducing valve. The newly added functional valve set is arranged on the basis of the existing negative flow control system without adding a new pump and is connected to the original flow control valve through the flow regulation and control pressure reducing valve to control the flow of a main pump,so that a newly added execution mechanism obtains the required flow, and the diversified requirements for system flow can be realized through added actions of the newly added execution mechanism. Thehydraulic system is simple, convenient to use and high in feasibility, and the application range of the original negative flow control system is effectively expanded.