Underground setting tool pressure starting system

The utility model discloses an underground setting tool pressure starting system. The underground setting tool pressure starting system comprises a central pipe, an underground setting tool, a piston, a safety diaphragm, a cup assembly, a stopper, a transmission coupling, a shell and a pressure bushing. The central pipe is capable of extending along a borehole, the piston is arranged outside the central pipe and comprises a piston part and a rod part, the stopper arranged at four sides of the central pipe and the piston jointly define a first liquid holding cavity and a second liquid holding cavity, the rod part is connected with the pressure bushing, the pressure bushing is adjacent to the shaft end b of an underground setting tool and probably contacts with the same, the stopper is adjacent to the shaft end a of the underground setting tool, there is one or more ports, the second liquid holding cavity is communicated with the borehole annulus through the port, the shell defines a third liquid holding cavity