The thermal imidation of fluorine-containing poly(amide-acid)has been investiga-ted by Tarsional Braid Analysis(TBA)．The results are discussed in tems of the molecular motion of polymer segments above its glass transition temperature，which is favourable to the diffusion vf small molecules and，therefore，has effect on the imidation reaction．The glass transition temperature increased from 120℃ to about 310℃ with in-creasing rigidity of the polymer chain by imidation reaction．Hence a reason

able productiun process of step-up cure is suggested．The multiple transitions including solvent evaporation，glass transition，secondary transition in glassy state and imMation reaction of pre-polymer in the TBA Spectra have been analyzed．The effect of solvent and water on imidation reactivn has been observed and explained with the above viewpoint．