Safety pressure relief device

The invention discloses a safety pressure relief device. The safety pressure relief device comprises a valve body, a pressing cap, a safety assembly and a piston assembly. The valve body is provided with a gas inlet and a discharge port, and the gas inlet is suitable for being connected with a gas cylinder; the pressing cap is detachably mounted at the upper end of the valve body; the safety assembly is arranged in the pressing cap and comprises a fusible plug and a first filter screen, the fusible plug is made of fusible alloy, and the first filter screen blocks the fusible alloy which is not liquefied; the piston assembly comprises a piston and a first spring, the piston is in sealing fit with the inner wall of the air inlet to form a valve, and the piston abuts against the lower portion of the fusible plug in a matched mode through the first spring. When the environment temperature exceeds a set temperature threshold value, the fusible plug is melted and passes through the first filter screen, the piston m