Abstract: Based on the demand of field project design, researches on characteristics of inner tank leak dynamic process of full-containment LNGstorage tank are made to build a leak source model describing the inner tank leak dynamic process and derive the equation of relationshipbetween leak liquid level height and leak duration based on the position of leak hole. A 16×104 m3LNG storage tank is taken as an exampleto make calculations and analysis under different operating conditions. The results show that the worst condition of the full-containmentLNG storage tank inner leak is the cracking at the bottom, where there is the shortest time from liquid leak to annular space.