Abstract: The phase transition expansion curve of high chromium forged steel roll after austenitizing at 1 030℃ and cooling at different rates was measured by using LINSEIS R.I.T.A L78 quenching dilatometer. The critical temperatures of the high chromium forged steel roll were determined by dilatometer method combined with metallographic test and hardness test, and the continuous cooling transformation (CCT) curves of the steel was drawn by Origin software, and then the test results were analyzed. The results show that the transformation of pearlite, bainite and martensite occurred in the continuous cooling process and the three phase transition regions were completely separated. When the cooling rate was greater than or equal to 1℃·s^-1, there was only martensite phase transition and the martensite phase transition starting temperature M_s decreased with the increase of cooling rate.