Field investigation was carried out along the Shanxi—Shaanxi Gorges in the middle reaches of the Yellow River. Typical flood slackwater deposit (SWD) of the late Holocene was identified at the Fotangcun site in the reach of Yonghe county. Sediment samples were taken after detailed observation of the texture and structure of the SWD profiles. Samples from the Guojiachuan site in the lower reach gorges of the Yanhe River, from the Holocene loess—soil at the Baishui loess tableland were also taken for a comparative study. Grainsize distribution, magnetic susceptibility, lossonignition and CaCO3 content were measured in the laboratory. The results show that the flood slackwater deposit of the Yellow River consist of sandy silt which were deposited from the suspended sediment in the floodwater. Therefore they were well sorted during the deposition.The flood slackwater deposit from the Yanhe River have the similar grainsize distribution to the Yellow River. However, the loess and palaeosol are much finner than the slackwater deposit and they have very high magnetic susceptibility. This indicates that the SWD of the Yellow River are fresh sediment with little weathering and pedogenic alteration. This study is of great significance to establish a longtime scale hydrological data for flood control and hydraulic engineering in the middle reaches of the Yellow River.