Abstract: The spiral-wound heat exchanger is the main low-temperature heat exchanger in the liquefaction process of natural gas. The flow characteristics of the working fluid on the shell side have an important influence on the performance of the heat exchanger. In order to study the falling film flow law of the working medium outside heat exchanger tubes, a three-dimensional falling film flow model was established and the numerical simulation was performed based on VOF (Volume of Fuid) method. The effects of Reynolds number and tube spacing on falling film flow were investigated on the heat exchangers under static and offshore sloshing conditions. It is indicated that average liquid film thickness decreases by 38.5% when the tube spacing increases from 4 mm to 10 mm. Under sloshing condition, appropriate increase of the tube spacing is beneficial to improve the distribution of liquid film. Improving the distribution of liquid film on the tube wall and reducing the liquid film thickness are favorable for improving the comprehensive performance of heat exchanger tubes.The studies on the liquid film on the shell side of spiral-wound heater exchanger under the condition of non-steady state can provide the reference for the structural improvement, energy saving & consumption reduction and offshore anti-sloshing design of heat exchanger.