The consequence of water gas leak was analyzed theoretically, and the Matlab software, combining the empirical formula of the pipeline leakage, was used to simulate the leakage phenomenon. The relationship between the influence scope of the water gas and the diameter of the pipe was obtained. According to the formula of the radiation of the combustion and explosion caused to the people and the equipments, the relationships of the thermal radiation dosage varying with the aperture ratio and explosion limit were gained for a instantaneous fire. The relationships of thermal radiation intensity varying with the aperture ratio and explosion limit were also got for a steady fire.