Abstract: Mixing the crude oil in a floating-roof tank with a rotary jet mixer during heating can increase the heat exchange so that the crude oil can be heated evenly. In order to study the effect of the rotation speed of a rotary jet mixer on the heating efficiency of crude oil, a 3D model of floating-roof tank with a capacity of 10 000 m³ was established through analyzing the heat exchange process of floating-roof tanks during heating to simulate the heating process of crude oil at different rotation speeds of the rotary jet mixer. The results indicate that, the rate of temperature rise in crude oil in the floating-roof tank mixed by the rotary jet mixer is significantly higher that without mixing, and the rate of temperature rise in crude oil increases as the rotation speed of the rotary jet mixer increases. However, there is critical point for the rotation speed. The rate of temperature rise of crude oil decreases when the rotation speed is too high. Conclusively, mixing can greatly improve the uneven temperature distribution of crude oil during heating, and the study results can provide a theoretical basis for enhancing the heating efficiency of a floating-rood tank in actual production.