Abstract: Determining the area of irrigation rotation is a key problem in irrigation design on sand dune.The concept and calculation formula of irrigation unit for plant sand-fixation on sand dune have been put forward in this paper by calculating intake rate,measuring intake process and deep loss rate as well as making repeated experiment with different discharge and different irrigation area.The irrigation unit is the maximum area of reasonable irrigation under certain discharge,definite region,definite soil or parent material and definite irrigation manner.For furrow or border irrigation the unit indicates the maximum reasonable irrigation area of single furrow or border;that of drip irrigation indicates the maximum reasonable irrigation area controlled by single submain line.Their empirical formulae in Taklimakan Desert have been carried out.

Key words: sanddune land, plant sand-fixation, irrigation unit, calculation formula