Abstract: The single hot compression tests of SPHC steel were performed using a Gleeble1500 thermomechanical simulator. The characteristics of strain induced transformation and ferrite grain refinement were investigated through analyzing the stressstrain curves and metallographic structures. The results show that very fine ferrite grains of about 1.6~4.6 μm can be obtained by the deformation at 750~830 ℃, due to the occurrence of SIFT. Decreasing deformation temperature leads to increase the chemical driving force for austenitetoferrite transformation and thus leads to refine ferrite grain. The size and volume fraction of ferrite grains decrease with increasing strain rate at the same strain level.