Abstract: Due to the harsh service environment of bearing steel, it must have high hardness, toughness, wear resistance and strength. Gleeble-3500 thermal simulation testing machine was used to study the effect of rare earth Y on the phase transformation and hardness of GCr15 bearing steel samples at different cooling rates. Through OM, SEM, EDS, hardness tester and other equipment, combined with Origin and Image J software, the data were processed and analyzed. The results show that rare earth Y increases the A_c1temperature of GCr15 bearing steel by 45.3 ℃ and the A_ccmtemperature by 14.8 ℃. At the low cooling rate, rare earth Y tends to concentrate at the grain boundary, which hinders the formation of network carbide and makes the network carbide become a fractured network, the thickness and volume fraction decrease. At the high cooling rate, there is no crack at the grain boundary, because the formation of rare earth sulfide changes the distribution of S impurity elements, reduces the segregation of S element at the grain boundary, purifies the grain boundary and improves the strength of the grain boundary. After the addition of rare earth Y, the hardness of GCr15 bearing steel can be effectively improved.