Abstract: Weir recovery technology has been widely used in dealing with marine oil spill. The theory of weir flow is presented to analyze discharge capacity of recovery weir in weir skimmer, and the reason of flow instability, which occurs to thin-walled recovery weir and results in decreased recovery efficiency, is ascertained. The curved practical weir is presented to enhance flow stability and recovery rate of thin-walled recovery weir, and design method of curved practical weir is provided, which lay the theoretical foundation for achieving more rapid and efficient oil spill recovery by weir skimmer.