The critical issue for a successful Sea Water Reverse Osmosis (SWRO) plant is pretreatment, which could provide consistent and high quality feed to SWRO membranes. In China, most pretreatment prior to SWRO use conventional ones, e.g. sand filtration, media filtration, cartridge filtration, et al, which have shown some drawbacks due to significant and unpredictable variation of seawater quality. For pretreatment of open seawater intake, membrane filtration may be a better choice. In this study, UF system utilizing hollow fiber membranes was used as pretreatment prior to SWRO desalination at Qingdao Jiaozhou Bay, the Yellow Sea in China. A different approach, focused on optimizing the design of a hybrid UF-RO system by maximum net product flow, i.e., an optimum correlation between filtration and backwash duration that can ensure best reliability of UF pretreatment was described. Operation of different recovery rate and flux of UF system was investigated to evaluate the performance of UF system. The results of the UF-SWRO system indicated that UF pretreatment could enable the RO pilot plant to be run stably and successfully. During the experimental periods, no chemical was injected into the UF-RO system, which showed that the UF-SWRO system performed well without any chemical cleaning.