We have newly developed high ozone resistance microfiltration (MF) module using polyvinylidenefluoride hollow tiber membrane which has high ozone resistance despite being organic material. A new filtration system using this MF module together with ozone can consistently provide 3 to 4 times higher permeate nux compared against the filtration without ozone for various types of feed water. This is because ozone decomposes or denatures a part of organic materials in the raw water and reduces fouling of the membrane surface.