The multiple pool fires may interact with each other when the fire occurs between two adjacent LNG storage tanks, which would aggravate the consequences of the accident. Figuring out the critical interval spacing which could cause flame merging is of great importance for designing the tanks. Aiming at 2000 m³ storage tanks and based on FLACS software, this paper numerically has investigated the flame temperature, pressure distribution, and flame shape of two LNG tanks with pool fires where the tank spacing are 7.6 m, 9.5 m, and 11.4 m. It is concluded that the multiple pool fires' consequence is the most serious when the spacing is 9.5 m, which has the highest both flame height and turbulence intensity. Also, the pressure difference between the center and two sides of the flame is the greatest. The flame is deflected in the vertical direction after being affected by the pressure difference. Besides, the flames finally merge together when the pressure difference reaches 86 Pa. The flame severity of multiple pool fires increases first and then decreases slightly with increasing spacing within 7.6m-11.4m. The flames no longer affect each other and can be regarded as two single pool fire when the spacing is greater than 11.4 m. The LNG tank spacing that determined during designing process should be larger than the spacing which would result in flame merging, so as to effectively reduce the consequences as well as the risks of pool fires.