Electroosmotic flow through packed beds filled with kaolin slurries conditioned with various chemicals (KCl, alum and polymeric flocculant etc.) was experimentally studied. A theoretical expression relating electroosmotic flux to physicochemical properties of the bed was derived and agreed with experimental data at low KCl concentration. When slurries were coagulated with high alum dosages without pH adjustment, a threshold electric field strength commenced electroosmosis flow, and a hysteresis phenomenon in the electric field strength dependent on electroosmotic flow were observed. However, when slurries were conditioned by adding polymeric flocculant, both the electroosmotic flux and its flow direction were qualitatively consistent with the prediction based on the measured values of zeta potential of particles.