Abstract: Polyanilinepolyimidepolyaniline (PANI-PI-PANI) composite films were in situ deposited on PI film matrix in dispersion polymerization. PVPK90, PVP-K30, CTAB and Tween20 were used as steric stabilizer and the stable effect of them on the morphology of the composite films were studied. When PVP-K90 was used as steric stabilizer, high quality composite films could be prepared. The UV and IR spectra confirmed that the surface layers of composite films were composed of HCldoped PANI and the composite films did not contain PVP-K90. When PVPK30、 CTAB and Tween-20 were used respectively as steric stabilizer, the composite films were weak in morphology. It showed that the good stable effect of PVP-K90 was not only related to hydrophilichydrophobic interaction and surface energy reduce, but also related to the maromolecular structure and the special interaction of PVP-K90，water and aniline, it could be explained by mechanism of oligomer deposited to nucleus.