Due to composition segregation and cooling speed,streamline or banded structure were often obtained in the thermal forming parts along the direction of parts forming.Generally speaking,banded structure doesnt decrease the longitudinal mechanical properties,so the secondary banded structure cant get enough attention.The effect of secondary banded structure on the fatigue properties of micro alloyed DG20Mn and 35CrMo steel was investigated using the axial tensile fatigue test of stress ratio of 0.1.The result shows that secondary banded structure was obtained in the center of the steel parts,because of the composition segregation and the lower cooling rate in center part of steel.Secondary banded structure has no significant effect on axial tensile properties of both DG20Mn and 35CrMo,but decreases the axial tensile fatigue performance of DG20Mn steel.This study suggests that under the high cyclic tensile stress,multi-source damage cracks in steel initiated by large strain of pearlite of secondary banded structure,which is larger than damage strain,is the major factor of the decrease of fatigue life of steel.