For analysis of prestressed concrete wall vibration character of cylindrical LNG tank on conditions of inner-tank leaking, the finite element analysis model of tank exterior wall of leak conditions is built and the modal analysis is carried out; then dynamic pressure on liquid storage equivalent with tank wall have the same acceleration of additional mass, natural frequency of teak wall is gotten; in state of semifluid and fluid filled, using methods of simulation of prestressed effect equivalent load, the natural frequency of the external wall of the central to the wave curve is achieved. The analyzing results show that: in state of fluid filled LNG storage tank, liquid is the largest effect on the frequency of prestressed concrete external wall. When liquid position is less than half the maximum reservoir depth, its natural frequency can be calculated by empty tank; when the liquid position is more than half the maximum reservoir depth, we should considerate that the liquid vibration has impact the vibration frequency of tank exterior wall; when different liquid position, the largest affection is 2.29% to natural frequency of prestressed wall.