This paper uses microwave technology to study the heating process of cargo oil in tanker side cabin under the static environment. The research is aimed to improve the heat transfer efficiency of cargo oil and solve the problems of uneven temperature distribution and energy consumption during the heating process of traditional crude-oil in oil tank. Based on the theory of microwave heating and heat transfer, the finite element simulation software is used to couple the microwave and temperature field during the cargo oil is heated to simulate the changing characteristics of the temperature field in static environment, and then verify the numerical results of the existing experiments. The simulation results show that the numerical results of this model agree well with the experimental data, and the error is in the range of 6.21-13.84%. Therefore, the accuracy of the numerical method can be verified. During the heating process, the absorption of microwave energy has a positive correlation with the electric field intensity distribution. The microwave field shows a “strong point” distribution characteristic. Heat transfer is accompanied by natural-convection and heat conduction, and the oil temperature distribution is more balanced under the combined effect, which shows that the microwave heating of oil tankers have certain feasibility. The results of this study can provide a theoretical basis for studying the heat transfer law of oil tanker cargo steam and microwave combined heating process.