Abstract: 28MnCr steel is used in the production of casings for deep wells. This study investigates the effect of rare earth cerium (Ce) on the continuous cooling transformation behavior of 28MnCr steel, providing a basis for formulating heat treatment processes, reducing costs and improving efficiency in the manufacturing of deep-well casings.The critical transformation temperatures and thermal expansion curves during continuous cooling of 28MnCr steel with 0 and 0.008 7% Ce were determined using a Formastor-F thermal expansion dilatometer. The room temperature microstructures at different cooling rates were observed using a Zeiss optical microscope. The continuous cooling transformation (CCT) curves of the tested steel were constructed. The effects of Ce on the critical transformation temperatures, phase transformation temperatures at different cooling rates, and room temperature microstructures of the 28MnCr steel were investigated. The results show that at a continuous cooling rate of 0.5 ℃/s, the microstructure of both test steels is a polygonal F (ferrite)+P (pearlite) structure. When the continuous cooling rate is between 1.0 and 5.0 ℃/s, the microstructure at room temperature is a B+F structure. When the continuous cooling rate is between 10.0 and 30.0 ℃/s, the microstructure is mainly B (bainite) +M (martensite), and when the continuous cooling rate is no less than 30.0 ℃/s, the microstructure obtained is mainly M. The addition of rare earth Ce expands the F+P transformation zone and narrows the B transformation zone, causing the M transformation zone to shift upward.