Due to the main composition of flammable gas in the tank of the sour gas field, the gas phase space in the tank is possible to form a mixed explosive gas in its special operation process.Therefore, the condition of combustible gas explosion in the tank is studied to prevent combustible gas.Gas explosion is of great significance.Based on the analysis of the production process and the related theory of the explosion limit of mixed gas,a suitable model and calculation method for the variation of gas explosion concentration in the tank is set up.The possibility of explosion and the way to avoid the explosion in the sour gas field are demonstrated through the calculation and prediction of examples.Under the current working mode, there are possible conditions for explosion formation in the process of water transfer from sour gas field water tank.The explosion limit can be calculated according to the mixture of inert gas and combustible gas.It is suggested that micro-positive pressure should be maintained in the tank, fire arresters be installed in the breathing tube, antistatic grounding be provided, at the same time, non-metallic pipes and equipment should be given priority to reduce the explosion risk.