The finite volume method and standard k − ε turbulence model are used to numerically investigate the heat transfer features of crude oil inside the floating roof tank under the hot oil spraying heating mode. The results indicate that this heat transfer process has the essential features of the thermal buoyancy jet flow. The jet flow is divided into the strong buoyancy, weak buoyancy and common buoyancy process according to Froude number of the jet flow. Bigger Froude number of the jet flow indicates stronger heat exchange strength and more uniform distribution of oil temperature. Smaller Froude number indicates stronger buoyancy, weaker heat exchange strength and more obvious hierarchical distribution feature of the oil temperature inside the tank. Two indices (efficiency and uniformity) are introduced and examined which could be of practical usage. According to the simulated result, higher nozzle speed and proper spraying temperature which results in a lager Froude number can achieve better heating effect by taking two previous indices as evaluation criterion. For the practical engineering usage, the spraying temperature and nozzle speed should be adjusted synchronously based on Froude number.