Silica particles were distributed in polyimide varnish solution and ultrasonic wave irradiation caused uniform coating of the particles. The particle-coating process was observed according to the Brunauer-Emmett-Teller surface area, and by thermogravimetric analysis, scanning electron microscopy, Fourier transform IR spectroscopy and energy dispersive X-ray spectroscopy. The resistance to the acid and alkali solutions was evaluated with inductively coupled plasma atomic emission spectroscopy. A comparison of the silica particles with and without a coating of 0.1 and 0.2 wt% polyimide showed obvious differences in silica dissolution behavior.