Accurate measurement on the volume of crudeoil is influenced by the change of oil temperature, the temperature distribution in the storage tank also has a very important significance on the tank safety management and operation. Starting with crudeoil temperature distribution in the storage tank, crudeoil temperature distribution of different locations on central crosssection in the storage tank was analyzed through the numerical simulation based on FLUENT. The results show that the temperature near the tank wall dropped rapidly at first at this early stage of temperature decrease, and the high temperature region was located in tow rectangular zones above the center of the section, presented two rectangular area. When the temperature field was tending towards stability, the high temperature region moved to the connection region in the bottom of the tank and the center of the section. Finally the high temperature region stayed in the bottom of the tank.