Effect of rare earth element Ce on behavior of high temperature deformation of IF steel was discussed.Different Ce content in IF steel were heated to 1250℃ for 5 min with a heating rate of 10/s at vacuum conditions,then cooled to 1100℃,1000℃,900℃,800℃for 30s with a cooling rate of 5/s and compressed by 50%with a strain rate of 10-2 s-1 and 1 s-1 by using a Gleeble-1500D thermo-mechanical simulation machine to get the true stress-strain curves.Finally,in order to observe the compressed microstructure compressed sample were cut apart along longitudinal direction of the sheets.Results show that with a low rate of deformation of IF Steel,the dynamic recrystallization is the main softening mechanism,at a high rate of deformation dynamic recovery is the main softening mechanism.Deformation resistance of IF steel with an increasing rare earth Ce content has an inhibitory effect on recrystallization.