A thermal simulation test machine was used to conduct high-temperature compression tests on two sets of 685 test steels with and without rare earths. Through linear fitting analysis and microstructure observation, the effect of rare earths on the high-temperature deformation behavior of 685 armored steel was studied. The results show that when the deformation temperature is 1000°C, La-Ce mixed rare earth can increase the deformation resistance of steel, and the influence varies with the amount of compression deformation, while at 1100°C, the rare earth has no obvious influence on the deformation resistance of steel. After adding rare earth, the recrystallization activation energy of steel is increased by 6.78%. Mixed rare earth (La-Ce) has an inhibitory effect on the recrystallization of steel. Using Origin8.0 software for regression analysis, a mathematical model of armored steel containing rare earths is established. The model has good curve fitting characteristics, and the calculated values are basically in agreement with the experimental values.