Abstract: Heating principle of tubular heater of crude oil is described in the paper.It is pointed out that the most effective method to increase the heat efficiency of tubular heater is to rationally decrease excess air ratio and flue gas temperature, while the best way to decrease flue gas temperature is to increase convection surface of the crude oil, not to install air preheater.It is considered that previous choosing the heat load of radiation chamber in heater design can cut down the workload of engineers.Analysis results show that adopting fin—tubes with smaller diameter in designing convection surface is the optimal choice.