In view of the calculation problem of structure strength of marine Liquefied Natural Gas (LNG) storage tank, a finite element analysis model is established with 18 m3 Type C LNG storage tank for inland vessel as an example. The load boundary conditions corresponding to heeling operation conditions are set up to make a simulation calculation, the stress concentration area of storage tank is concretely analyzed, and the structure strength of storage tank under different heeling operation conditions is checked. The results show that the stress intensity of each member of storage tank is within the allowable value, but the phenomenon of stress concentration is easy to occur in the local structural discontinuities. The research results can provide reference for the structure design of LNG storage tank on relevant ships.