To a seawater reverse osmosis (SWRO) plant, an appropriate pretreatment procedure is one of the most important factors for its steady and safe performance. Many researchers have shown their interest in replacing conventional seawater pretreatment with ultrafiltration (UF) because of the stable product water quality it offers. The purpose of the pilot testing was to evaluate two inside-out UF modules (Module A and Module B) used for pretreatment of high-turbidity seawater after coagulation. A pilot-testing UF system was set up at the seashore on the southeast coast of China. Operation parameters such as flux, backwash (BW) time, BW frequency, and frequency of chemically enhanced backwash were varied. Modules A and B were operated at a flux ranging from 69-95 L/m(2)h and 86-130 L/m(2)h, respectively; the corresponding transmembrane pressure was 0.18-0.25 bar and 0.30-0.45 bar. filtrate(SDI15) of Module A was maintained below 3 during the test, and the permeate(SDI15) of Module B was less than 3.37. These permeates met the requirement of the feed water quality of SWRO. A NaClO concentration of 6 mg/L proved to have little influence on decreasing the filtrate(SDI15). Other parameters of water quality such as total Fe, COD, colloidal Si and total bacterial count were also measured. The UF trial was successful in achieving stable membrane permeability.