The grain growth of dynamic strain induced transformation (DSIT) ferrite during post deformation cooling for two prior austenite grain sizes was investigated by hot torsion test. The results showed that the prior austenite grain size affected the distribution of DSIT ferrite nucleation sites and the subsequent coarsening behaviour of the grain boundary (GB) and the intragranular grains (IG) nucleated during post deformation cooling. Moreover, an increase in post deformation cooling rate led to decrease in the coarsening rate and the final ferrite grain size.