Accurate prediction of oil temperature in a large floating roof oil tank is very important for both strategic and commercial storage of crude oil.The oil temperature in the tank is influenced by many factors such as atmosphere temperature，thickness and conductivity of insulation coat，solar radiation intensity，soil physical property etc.In this study，these factors are considered in the model establishment to predict the temperature field of a large floating roof oil tank.A SIMPLE code is developed to calculate the coupled heat transfer among buoyancy chamber，oil，soil and insulation coat.The effects of solar radiation and thickness of insulation coat on oil temperature are studied.The numerical results are compared with and agreed well with field test data.