Abstract: This paper introduces the working principle of water sealing fire resistance and explosion venting device to ensure the safety of low concentration gas transportation through water sealing fire resistance and over-pressure automatic explosion venting; this paper analyzes the problems existing in the vertical structure of water sealing fire resistance and explosion venting device for DN1 000 mm gas transmission pipeline, and determines that ZGZS1000 water sealing fire resistance and explosion venting device adopts horizontal structure. Then, based on the principle of gravity settlement and the safe critical velocity of gas, through trial calculation and verification in turn, and considering the economy, the cylinder diameter and cylinder length of ZGZS1000 water sealing fire resistance and explosion venting device are designed. Subsequently, combined with the installation position, explosion pressure and explosion venting pressure of water sealing fire resistance and explosion venting device, the strength and thickness of the cylinder are designed. Finally, a water level control system composed of three water level sensors, a water supply electric valve, a drainage electric valve and a water level controller is designed to realize the automatic control function of water level, so that the water seal height of water sealing fire resistance and explosion venting device is always kept within the effective fire prevention range.