Rainwater harvesting is a process by which rainwater collected from rooftop or other catchment is purified sothat the water can be directly or indirectly used by human beings for beneficial uses. As rainwater is increasingly consideredfor high quality purposes, membranes have gained an important place in rainwater treatment. It has advantages such as theproduction of high quality water, small footprint, and affordable energy consumption. Nevertheless, membrane fouling is regardedas a serious problem similar to the cases of water treatment and wastewater reclamation. In this study, we appliedmicrofiltration (MF) membranes for rainwater treatment. In addition, a low pressure ultraviolet (UV) process was also use asa pretreatment to control notonly. To quantify the effect of UV on organic matters, both total organic carbon (TOC) andUV absorbance (UVA) were measured. Moreover, the effect of UV pretreatment on membrane fouling was investigated.Experimental results indicated that the pretreatment of membranes using LPUV was effective to control fouling of MF membranesonly when the rainwater was contaminated by algae. This was attributed the reduction and modification of organicsafter UV treatments. It is likely that the UV/MF process is a promising option for water treatment in decentralized watertreatment such as micro water grid systems.