Abstract: Hot compression experiments were carried out for Nb-V microalloyed non-quenched and tempered steels on the Gleeble-3800 thermal simulation machine,and the effects of deformation (forging) process on the microstructure of test steels were studied by OM and SEM. The results show that low temperature (850 ℃) forging with deformation degree of 15% could facilitate the grain refining of Nb-V microalloyed non-quenched and tempered steels and increase the ferrite content. The cooling rate reducing was conducive to the growth of proeutectoid ferrite. The addition of Nb into the steel could improve the recrystallization temperature and refine the microstructure. Meanwhile,the precipitation of carbonitrides promoted the proeutectoid ferrite forming,which improved the toughness of Nb-V non-quenched and tempered steel.