In order to study the temporal and spatial distribution of gas in the event of gas leakage in overlying oil tanks, based on the turbulence � - � standard model, the numerical simulation of oil and gas leakage diffusion of a tank chamber in an overburden oil tank is carried out. The dispersion trajectory of hydrocarbon gas after oil tank leakage is explored and the variation law of hydrocarbon gas concentration with time in horizontal and vertical direction in the covered oil tank chamber is analyzed. The results show that the hydrocarbon gas dispersion process is divided into quasi-static period, gradient rising period and stable period. The quasi-static period is the same at the same height, and the higher the height, the longer the quasi-static period will be. In the gradient rising period, as the height increases, the smaller the hydrocarbon gas concentration growth rate is. In the disturbance area, the closer to the leakage at the same height, the higher the hydrocarbon gas concentration growth rate will be. In the stable area, the faster the volume concentration growth rate, the same the hydrocarbon gas volume concentration growth rate is with the same height. The lower the hydrocarbon gas volume concentration is with the increase of the height, the time required for the hydrocarbon gas volume concentration in the tank chamber to reach the stable period is the same. The closer to the leakage at the same height within the disturbance area, the greater the hydrocarbon gas volume concentration will be and the relative leakage point is symmetrical, but the hydrocarbon gas volume concentration in the stable area is the same with the same height. It is also found that when hydrocarbon gas volume concentration is lower than the safe hydrocarbon gas volume concentration over a certain height, namely the safe zone. The research results are of great significance for the safe handling of hydrocarbon gas leakage in covered oil tanks.