Sloshing is an inevitable problem for the membrane-type liquefied natural gas (LNG) tank. The structural fatigue and failure inside the liquid tank may be caused by violent sloshing impact loads, resulting in leakage, fire and explosion of flammable and explosive liquid and thus incalculable loss. It is important to accurately predict the sloshing impact load for the safety assessment of the liquid tank. The sloshing of two different mediums (water and LNG) has been numerically calculated based on computational fluid dynamics (CFD) method. The sloshing impact loads of the two mediums (water and LNG) are analyzed to propose the feasibility of the sloshing test with water instead of LNG. A sloshing model test is then designed for a membrane-type LNG tank with water to establish a complete sloshing test system for the sloshing test with water. In the six degree-of-freedom sloshing test of the liquid tanks, the pressure distribution inside the liquid tank and the local pressure characteristics are tentatively analyzed by combing the single sensor with the clustered sensors, providing references for the structure design of the liquid tank.