The high speed elimination process of suspended solid was investigated to treat the pulp waste water by using surface modified magnetite particle and magnetic power. The effects of the various aluminum salts such as Al(NO3)3·9H2O, AlCl3·6H2O, Al2(SO4)3·13～14 on the COD, BOD and suspended solid were systematically studied. It has been found that the 2.0 wt% of Al was most effective for the modification of Fe3O4 powder and then best for the treatment of pulp waste water. Optimum quantity of modified magnetite in this study was 12 wt%, and aging time was found to be 12 hours. Comparing with the conventional process, the required time for SS removal was drastically decreased. BOB and COD were also effectively removed when applied to the pulp wastewater.