The microstructure of a bainitic steel after different cooling rates has been investigated by transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD). The effect of cooling rate on the intermediate transformation microstructure was studied. The results showed that the final microstructure contained complex mixture of bainitic ferrite, granular bainite and polygonal ferrite. There was mainly lath-like bainitic ferrite at fast cooling rate (20Ks-1), while microstructure in samples cooled with intermediate rates (8~15 Ks-1) contained bainitic ferrite and granular bainite. When cooling rate decreased to less than 5Ks-1, polygonal ferrite occurred.