Abstract: The thermal simulation tests of the non-annealing 10B21 cold heading steel with different temperatures,deformation and cooling rates were carried out to study the effect of controlled rolling and controlled cooling on the microstructure. The results show that the deformation induced ferrite transformation by low-temperature, large deformation rolling and slow cooling at 0.8 ℃/s make the volume fraction of ferrite increase from 71.69% to 79.82%, and part of the pearlite changes from flake to granular, which softens the wire rod online and achieves the requirement of non-annealing.