Effect of water back-flushing period (FT) was investigated in hybrid water treatment process of carbon ultrafiltrationand polypropylene (PP) beads coated with photocatalyst, and membrane effect was studied by comparing the previousstudies with carbon microfiltration or alumina ultrafiltration, microfiltration membranes. FT 6 min was the most effectiveto control initial membrane fouling and optimal condition because the membrane fouling resistance was low until initial60 min and the maximum total permeate volume was acquired at this FT. The turbidity treatment efficiency was high beyond98.6%, and did not depend on FT, which was same with the previous result of carbon or alumina microfiltration. Theorganic matters treatment efficiency was the highest value of 98.2% at FT 6 min, which was almost same trend with theprevious result of alumina microfiltration. Then the organic matters treatment efficiency of carbon microfiltration was theminimum at no back-flushing (NBF) and increased as decreasing FT, but that of alumina ultrafiltration was the maximum atNBF and also increased as decreasing FT. Therefore it means that water back-flushing effect on the organic matters treatmentefficiency had a different mechanism depending on pore size in spite of the same material membranes.