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Magnesium alloy sheet rolling has special control requirements for the temperature of the work rolls, in this paper, the temperature control of the rolls was controlled by fluid-solid coupled heat transfer. Based on the finite difference method, a differential model for the heat transfer process of roll and thermal oil was established, which was complemented by the corresponding experimental verification. A fluid-solid coupling heat transfer model was also established by FLUENT, giving the roll temperature rise curve, the surface temperature and the cross-section temperature distribution during the heat transfer process. The results showed that the temperature near the roll operating side is the highest and the temperature decreases gradually from the operating side to the driving side, and the temperature difference range between the operating side and the driving side is 5-12°C and is almost unaffected by the fluid temperature and speed. The maximum temperature difference between the inner wall and the outer wall of the roll is 6°C, which can be considered that the radial temperature distribution is even. Under different fluid temperature and velocities, the temperature of the roll rises with trend of decreasing rate, and when the fluid temperature rises and the velocity increases, the temperature rise of the roll becomes faster. After the roll stops heating, its surface temperature does not begin to drop immediately and continue for a period of time, which was about 5-8 minutes, and the temperature and speed of the fluid have less effect on the extended time. The calculated values of the average roll surface temperature agree well with the experimental values, the maximum relative error is 8.3%, which verifies the correctness and effectiveness of the finite differential model, and as part of the magnesium alloy plate rolling model, it is conducive to the isothermal control of the roller in the rolling process and realizes isothermal rolling control of magnesium alloy plate.