Two experiments were carried out on the same compact strip production (CSP) line, which differs in that one of them experienced γ→α→γ* thermal history. The differences in microstructure, precipitation, misorientation etc between two experiments were investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron back-scattered diffraction (EBSD) and positron annihilation technique (PAT). The carbon concentration in matrix is more inhomogeneous in the experiment than that with γ→α→γ* thermal history. The specific precipitation characteristic in the experiment without γ→α→γ* thermal history is discussed on the basis of different carbon diffusion behavior and interaction between dislocation and excess carbon.