Abstract: The evolution process of DIFT (deformation induced ferrite transformation) microstructure in low carbon steel at the temperature slightly higher than Ar3 as well as the effect of subsequent continuous cooling/holding process at different temperatures on DIFT microstructure was investigated using thermo-simulator. The experimental results showed that although the volume fraction of DIFT microstructure increases with increasing true strain, such an increase hasn't found in a part of austenite even after a heavy deformation. The deformed austenite is transformed into coarse ferrite in a static transformation mode during the subsequent cooling, thus forming a mixed crystal microstructure. Both the experimental and theoretical calculation results confirm that, during the continuous cooling after deformation, there is a critical temperature below which the grain growth in DIPT microstructure will stop. During the holding at different temperatures after deformation, the grain growth will become very slow when the holding temperature is lower than a certain temperature.