The utility model relates to a modularized design high pressure operating mode depression bar unstability triggers type relief valve. The essential element includes valve body, piston, inside lining, valve gap, needle cage, elongate rod and nut. This device trigger the euler law of having used the elongate rod unstability. And elongate rod's unstability advocates to come from the piston in pressure medium effect thrust down, and when thrust when pressure medium is used in the piston on was greater than elongate rod's critical load, elongate rod took place unstability forfeiture bearing capacity, and the holding power that the piston lost elongate rod is broken away from sealed on the valve body inside lining by the pressure medium promotion, installs and converts the purpose that the state of opening has reached the pressure release into by the closed condition. Effective lifting surface area that can the rational design piston makes it can be applicable to high -pressure operating mode. Simultaneously parts such as piston, inside lining and valve gap are designed into the module, break down or change convenient and fast when wearing and tearing.