Variations of porosity and specific local filtration resistance in cake filtration were studied in a filter cell. samples used were slurries of CaCO₃, Talc(I) and Talc(II) and diatomite filter aids, which were used by body feed-ing and precoation. From the experimental result, the porosity of filter cake decreased and the specific local filtration resistance in-creased with increasing pressure. The addition of filteraids increased the porosity of filter cake and it resulted in de-creasing the specific local filtration resistance.