In order to improve the performance of sponge iron for removing dissolved oxygen, sponge iron was originally modified by chemical replacement copper plating and the optimum modifying condition was obtained by orthogonal experiments. The effect of each modifying condition on the dissolved oxygen (DO) level in the outlet treated by modified sponge iron was investigated. The operating condition of packed bed was also investigated. The results showed that the performance of modified sponge iron for removing DO was improved obviously. The optimum modifying conditions were as followed: the concentration of CuSO4·5H2O was 40 g/L, citric acid was 80 g/L, the concentration of sodium tartrate was 45 g/L, the concentration of H2SO4 was 60 ml/L, modifying time was 120 s and temperature was 50 °C. DO in outlet water from optimum modified sponge iron packed bed increased initially and then decreased with increasing each modifying condition respectively. DO in outlet increased by increasing the flow rate or decreasing the bed height, and there were no DO detected when the packed height was 35 cm and the flow rate was not above 32 L/h.