Processing of polyimide (PI) from precursor polyamic acid (PAA) solution involves simultaneous imidization, evaporation of solvent and crystallization, so imidization process influences the final properties of PI. The residual stress at the interface between the most popular PI (PMDA-ODA) and the aluminum substrate was measured by X-ray diffraction method and the relationship between the microstructure and the mechanical properties was investigated for PI with different imidization processes. The residual stress and the mechanical properties of PI depend on the imidization process. The skeletal structure is suggested to be changed by the amount of residual solvent during imidization process, which brings the difference in the residual stress.