Spherical silica particles were dispersed in a polyamic acid varnish (PAAV) solution, and ultrasonic wave irradiation resulted in high-speed condensation of conversion to polyimide and in coating of the silica particles. The imidization reaction was verified by Fourier transform IR analysis, thermogravimetry, gel-permeation chromatography and moisture analysis. In addition, the particle coating was observed by transmission electron microscopy. Adsorption of polyimide acid onto the surface of the silica particles while achieving an imidization reaction by ultrasonic wave irradiation has been clearly shown to enhance the rate of the imidization reaction.