Generally, a sodium hydroxide solution containing hydrogen peroxide is used to dissolve molybdenum-benzoinoxime complex in the a-benzoinoxime precipitation method. However, the existence of residual hydrogen peroxide in the solution will interfere with the adsorption of ⁹⁹Mo by alumina. The separation of molybdenum with only sodium hydroxide solution was carried out in this work. A simulated solution consisted of 50 ppm molybdenum and 1 M nitric acid was used. Adding benzoinoxime with the 20-weight ratio of benzoinoxime to molybdenum produced molybdenum-benzoinoxime complex. Molybdenum was separated from molybdenum-benzoinoxime complex by reaction during 5 minutes using distillated water, 0.1 N, sodium hydroxide solution, and sodium hydroxide solution containing 1 wt% hydrogen peroxide. As results, molybdenum was separated over 97%, and the separation efficiency was not different with the case of solution containing hydrogen peroxide. It is estimated that hydrogen peroxide acts to accelerate dissolution rate of benzoinoxime and does not affect to separate molybdenum from molybdenum-benzoinoxime complex.