The invention relates to an experimental facility of in-situ determination of a vertical permeability coefficient of sediments. The experimental facility comprises a water storing standpipe, connecting flanges, a sealing gasket, a steel gauze element, and a sediment cavity, wherein the water storing standpipe is located above the ground, and is used for storing water in an experiment; each connecting flange comprises a water storing standpipe flange and a sediment vessel flange, and is used for connecting the water storing standpipe and the sediment cavity; the sealing gasket is located between the two connecting flanges and is used for sealing a connecting part of the water storing standpipe and the sediment cavity so as to prevent leakage; the sediment cavity is located below the ground and is used for infiltrating and discharging rinsing water in an experimental section. At the same time, the invention further provides a method for using the experimental facility to conduct in-situ determination of the vertical permeability coefficient of sediments. The experimental facility is used for conducting measurement of the permeability coefficient, has a wide range of application, is simple in facility installation and convenient to operate, can be used directly in the conduction of a field in-situ experiment, and is capable of accurately measuring the vertical permeability coefficient of the sediments.