Abstract: Hot-compression test of as-cast GCr15SiMn bearing steel was carried out on a Gleeb-3500 thermal simulator. The effects of deformation temperature (1 223-1 423 K) and strain rate (0.1-10.0 s^-1) on flow stress were studied, and the microstructure was observed. The flow stress constitutive equation of the test steel was established by fitting the experimental data on the basis of the Arrhenius equation given by TEGART and SELLARS, and was verified. The results show that when deforming under test conditions, all the flow curves of the test steel showed a dynamic recrystallization characteristic; increasing the deformation temperature or reducing the strain rate could reduce the flow stress. At the strain rate of 1.0 s^-1, increasing the deformation temperature helped the dynamic recrystallization of the test steel and coarsened the grains. At the deformation temperature of 1 423 K and the strain rates of 0.1-1.0 s^-1, the greater the strain rate, the finer the dynamic recrystallized grains. The peak stresses were predicted by the established flow stress constitutive equation. The average relative error between the calculation value and the test value was 0.393%, indicating that the constitutive equation was relatively accurate.