Abstract: Regarding ultra-low carbon IF steel with carbon content of 12 mg·kg-1 as the research subject, effects of cold rolling reduction and annealing process on recrystallization and mechanical properties of ultra-low carbon IF steel were studied by Gleeble3500 thermal simulation test machine combined with other experiment methods such as hardness test and microstructure observation. The results show that with different rolling reductions of 75%, 79% and 84%, the recrystallization temperatures of tested steel were 691, 688 and 685 ℃ respectively, which were a little lower than that of the IF steel with carbon content of 0.002 4wt%. The recrystallization temperature decreased a little with the increase of cold rolling reduction rate. The strength decreased and elongation raised with the increase of annealing temperature. To take annealing at 830 ℃ as an example, the holding time of 60-180 s could ensure recrystallization completion.