Catalyst fixed-bed method was studied for the dissolved oxygen(D.O.) removal in makeup water. Through experiments of a catalytic liquid-solid reactor and experimental data, its modelling, it is found that about 13 l Pd-catalyst based on hydrophobic polymer resin is required to reduce D.O. concentration of 10 l/min process water from 8000 ppb to below 10 ppb. Detail design of D.O. removal process employing polymer catalyst resin and hydrogen was carried out and a portable D.O. removal equipment was manufactured based on its design. This equipment was manufactured with treating capacity 10 l/min water and has shown a good performance of reducing D.O. concentration of 8 ppm in the water to below 10 ppb. As a result of investigation about the direct application of D.O. removal process to nuclear power plants, the condensate storage tank has been chosen as the most proper place for installation of D.O. removal equipment in nuclear power plants since the tank is located to directly influence water quality of reactor system and the equipment can be easily attached to the condensate tank without any major modification of existing plants. (Author).