Abstract: Effects of deformation temperature, deformation and holding time after deformation on recrystallization behavior of X70 pipeline steel used in submarine were studied by thermal simulator. The results show that when deformation was 25%, dynamic recrystallization temperature of the tested steel was 1 000-1 020 ℃, austenite grain size could be refined to 33 μm. Under the condition of deformation temperatue of 980 ℃, dynamic recrystallization happened at deformation range of 25%-30%, dynamic recrystallization completed basically when deformation was 30%. Grain size decreased with the increase of deformation. When deformation temperature was 980 ℃, deformation was 25% and holding time was 5 s, tested steels started to static recrystallization, the static recrystallization completed basically after holding 30 s. At the moment, austenite grain size was minimum and up to 41 μm.