The water-wind erosion crisscross region, located in northern Loess Plateau, is a typical ecologically fragile area. Soil desiccation occurs frequently under artificial shrubs and grass. The formation of dried soil layer (DSL) affects eco-hydrological cycle and threatens vegetation construction and ecological stability. To understand the soil desiccation process under artificial shrub and grass and to determine their suitable planting years, dynamics of soil water content and aboveground biomass with growth year for caragana and alfalfa were analyzed in the Liudaogou catchment. The results showed that soil water was consumed strongly and decreased rapidly under 2-8-year old caragana and 1-7-year old alfalfa. After then, soil water was relatively stable, changing slightly between 8.2%-9.0% under caragana and 8.5%-10.5% under alfalfa, respectively. The DSL was develop at depth of 1-1.4 m under 4-5 year-old caragana. The DSL reached 2.4 m depth, and the thickness of the DSL was 1.4 m under 6 year-old caragana. The depth of DSL exceeded 4.0 m under 9-12 year-old caragana. There was no desiccation under 2-4 year-old alfalfa, however, the DSL reached at 3.6 m depth and the thickness was 2.6 m at the end of growing season for 5 year-old alfalfa. The depth of DSL exceeded 4.0 m after 7 year-old alfalfa. Therefore, in order to decrease the risk of DSL formation, it is suggested that the growth years of caragana and alfalfa should not exceed 6 and 5 years, respectively. Their corresponding maximum dry biomass is about 5050 kg/hm² for caragana and 1980 kg/hm² for alfalfa, respectively. The results can provide scientific basis for management of artificial vegetation and regulation of DSL in northern Loess Plateau.