Abstract: The continuous cooling transformation (CCT) diagrams of austenite non-deformation and deformed at 950 ℃ were constructed by means of a combined dilatometry and Vickers-hardness measurement for a weathering steel.Optical microscope and TEM were employed to investigate the influence of cooling rate,deformation process on the transformation behavior and microstructure.Results show that the deformation promotes the area of ferrite move towards top left corner,leading to the increase of critical cooling rate obtained ferrite plus pearlite.The deformation on austenite stifled the growth of bainitic ferrite by tangled dislocations resulting the refinement of microstructure.Lath-like microstructure observed at the cooling rate above 15 ℃/s mainly is revealed to consist of bainitic-ferrite with cementite.Granular microstructure observed at the cooling rate ranging from 5-10 ℃/s is characterized to be martensite-ausenite constituent islands.