Abstract: A new type of water-cut test device with offline sampling detection function for high water-cut oil wells was developed and applied in an offshore oil field. The results of the filed study on the offshore platform showed that for the high water-cut oil wells with water-cut larger than 90%, four layers of composite oil-water separation membrane should be used for water content determination, and the determination time should be within 15 min so that the percentage change of the determination result is within ±1.0% compared with the centrifugal water content data, and the error of the determination result is within ±0.2% compared with the water content data of professional institutions, and the determination result is closer to the field production data. The operation of new water-cut test device is intelligent and easy to operate. The device reduced the impact of well fluid fluctuations using sampling volume amplification, realized the rapid oil-water separation using a complex oil-water separation membrane and vacuum pump, and prevented the adhesion loss of crude oil in the process of produced fluid transfer using a detachable sampling tank, prevented the adhesion of crude oil using superhydrophobic oil coating, avoided the error of volume reading using the weighing module so that the measurement of water content was more accurate and faster. The new water-cut test device meets the field demand for more accurate, faster, and more convenient determination of water content in high water-cut wells, which is conducive to the later adjustment of oil well production fluid optimization and lateral drilling decision.