Abstract: The floating roof tank is the main equipment for oil storage. To figure out the temperature distribution laws of oils in the tank and accurately predict the oil temperature change is of great significance to guarantee the low-consumption safe operation of tank farms. In this paper, a 5×10⁴ m³ floating roof tank was taken as the test object. And the change characteristics of crude oil temperature field inside the tank were investigated by means of field temperature track and measurement. It is shown that when the ambient temperature is lower than the oil temperature, the temperature inside the tank displays the anti-bathtub curve, and there is an obvious core constant temperature zone. When the ambient temperature is higher than the oil temperature, the temperature inside the tank presents the thermal conductivity distribution, and the core constant temperature zone disappears. The research results can provide the technical basis for the energy saving and emission reduction, the scientific establishment of the floating roof tank heating operation scheme and the prevention of condensing tank accident. (3 Figures, 1 Table, 21 References)