The aim of this research is to investigate the removal conditions of iron and manganese ions from groundwater by oxidation under aeration and chlorine oxidation, and microfiltration (MF). Pilot-scale experiments were executed in Chang-Hua water treatment plant. The raw waters contained iron (0.4 mg/L) and manganese (0.5 mg/L) ions were oxidized by chlorine and followed the filtration of hollow fiber PTFE-MF. The oxidized metal ion particles on membrane under appropriate backwash were also investigated. The particles size and treated water quality were carefully examined. The experimental results indicated that the concentration of the residual Mn ions reached 0.1 mg/L in treated water at initial operation period. However, it was decreased to less than 0.01 mg/L after two weeks processing time. The SEM and EDS analysis of oxidized metal particles under each process illustrated that those particles accumulated on membrane enhanced the Fe and Mn ions removal, which were caused by the auto-catalytic activity of them in the accumulated layer on membrane. Moreover, the membrane operation pressure over 120 kPa was suggested to active backwash process. The appropriate conditions were considered using sulfuric acid at pH value equal to 8 ~ 9.