In the heating process of traditional oil tanker oil, the thermal efficiency of the oil is not high, the heat loss is large and the operation process is complicated. In order to obtain better heating effect of the oil, the heating efficiency of the oil is improved. Based on the theory of heat transfer and microwave technology, the temperature field of electromagnetic field and fluid heat transfer was coupled. The finite element software COMSOL was used to simulate the temperature field variation characteristics of static underwater microwave heating oil, and the numerical simulation results of existing experiments were verified. The results show that the numerical simulation results of the model agree well with the experimental data, and the accuracy of the numerical method is verified. The distribution of the temperature field of the oil absorption in the heating process is consistent with the electric field distribution, and the absorption capacity of the microwave in the oil medium. Attenuation, vertical oil temperature difference, the upper surface oil temperature is the highest, the microwave absorption capacity is the largest; the whole cabin oil temperature field changes more evenly, indicating that the oil tanker oil heating method is feasible, also for the study of oil tanker cargo steam and Microwave composite heating technology provides a theoretical basis.