Precipitation plays an important role in vegetation establishment and plant growth, species composition and community structure and biomass distribution. With the intensification of global climate change, the effect of annual rainfall and its pattern on vegetation is getting more important. To clarify the response of sandy vegetation to precipitation (P) change,a device was used in a field experiment to control precipitation amount in Horqin Sandy Land. The height, density and coverage, species composition, above-ground and below-ground biomass of the vegetation were surveyed at 48 quadrates (50 cm×50 cm) once a month from May to July. The results showed that (1) Change of P had a significant effect on the average height, density and coverage of the sandy land vegetation. The rainfall in May is 19.2 mm and the coverage is higher in the plots with P added by 30% than that reduced by 30% and 60%, significantly. And there is a significant difference between P addition by 60% and reduction by 30%. When P added by 60%, the average density was deceased by 15.4%, but it was increased by 15.3% when P reduced by 30% compared with the control. In June, the rainfall was 96.8 mm, when P reduced by 60% and 30%, the average height was decreased by 8.8% and 2.3%, respectively. and the average height was increased by 6.8% and 1.4% when P added by 60% and 30%, respectively. The coverage is higher when P added by 30% than reduced by 30% significantly, and the vegetation coverage, compared with the control, was correspondingly increased by 19.7% and decreased 60.5%, respectively. Coverage was significantly increased in plots with P added by 60% than that reduced by 60%. The average plant density was increased by 8.90% when P added by 30%, and decreased by 14.2% while P added by 60%. (2) The effect of P change on diversity index and evenness was not significant within one year but the abundance index was influenced significantly in only July. There is a significant difference between P reduction by 30% and addition by 30% and 60%. The species richness presented a decrease trend with P addition. (3) P change had a significant effect on the aboveground biomass. When P added by 30%, the aboveground biomass was increased and maximized at 167.94 g/m² and the minimum was 68.37 g/m². The underground biomass was increased significantly with P addition. The ratio of underground biomass to aboveground biomass of all treatments was increased. (4) The underground biomass of the sandy land vegetation was mainly distributed in 0-20 cm and 20-40 cm soil layers, accounted for 52.7% and 42.65%, respectively. The distribution of roots in 20-40 cm soil layer was increased significantly with P addition, and increased slightly when P reduced by 60%. The underground biomass in 40-60 cm was increased when P reduced by 60% and added by 60%.