The UV/Fe(Ⅲ) process is a new combined process for treating heavy metal complexes. This process first releases free metal ions through the replacement of Fe(Ⅲ), then, it degraded the organic ligands via UV irradiation, and finally, heavy metals were removed by alkaline precipitation. In this study, heavy metal complexes, Cu(Ⅱ)-EDTA and Ni(Ⅱ)-EDTA, were removed by UV/Fe(Ⅲ) process. Through the comparison of removal effects and mechanism analysis, the internal mechanism of the difference in removal effects of the combined process was described, and the corresponding optimization scheme was proposed. The results showed that the removal efficiency of Cu(Ⅱ)-EDTA and Ni(Ⅱ)-EDTA was quite different, and the removal rates of Cu and Ni were 70% and 41%, respectively. The main reason for the difference in removal efficiency between Cu(Ⅱ)-EDTA and Ni(II)-EDTA was determined through high-performance liquid chromatography (HPLC), spectrophotometric analysis, and benzoic acid (BA) probe experiments, showing that Fe(Ⅲ) had a noticeable difference in displacing Cu(Ⅱ) and Ni(Ⅱ), with replacement rates of 85% and 22%, respectively. Optimal Fe(Ⅲ) dosages and reaction temperatures were separately optimized for the Ni(Ⅱ)-EDTA replacement process. The results showed that the reaction temperature optimization can significantly improve the Fe(Ⅲ) displacement efficiency on Ni(Ⅱ)-EDTA. When the reaction temperature was increased to 35 ℃, the removal efficiency of Ni was increased from 41% to 60%. The reaction temperature is very important for the removal of Ni(Ⅱ)-EDTA by UV/Fe(Ⅲ) process, proper heating is helpful to increase the replacement rate and further improve the removal efficiency.