In order to reduce dielectric constant of polyimide, preparation of porous films assembled by polyimide nanoparticles was investigated. We utilized the electrophoretic deposition of polyimide nanoparticles to prepare porous low dielectric constant (low-k) films possessing voids between particles. The films thickness was controlled in the range of 500nm similar to 5 mu m by changing the dispersion concentration and applied voltage. Porous morphologies were confirmed by SEM observation. As a result, dielectric constant of the film decreased to 2.32, 14% lower than that of the bulk polyimide film, due to the introduction of air voids into the matrix. This is the first report showing a promising approach with high processability for porous low-k polyimide films.