The kinetics for the oxidation reaction of ferrous ion in alkaline solution in with the dissolved oxygen was determined using initial rate method. The oxidation was conducted by injecting the ferrous ion into NaOH solution and the reaction orders in terms of oxygen consumption were the first order with respect to the ferrous ion concentration but varied with the alkali and the dissolved oxygen concentration. The deflection of reacion order with respect to alkali concentration was found to occur near 0.025 mole/l NaOH concentration. The rate equations for the oxidation were two types according to the temperature level ; one of these was -d[O₂]/dt=k[Fe^II][OH^-]^½/[O₂]^¾/K_FeOH⁺+[OH^-]） bellow 30 ℃ and another -d[O₂]/dt=k"[Fe^II][OH^-][O₂]^1/2/（K_FeOH⁺+[OH^-]) at 40 ℃. The activation energy for the oxidation of ferrous ion was 6.8 Kcal/mole. Amorphous iron oxy-hydroxide(δ-FeOOH) which had produced as reacting the iron sulfate to the NaOH in the aforementioned solution was confirmed by the X-ray diffractometer and the IR spectrophotometer.