Abstract: Based on the data from underground water monitoring,meteorological measuring and fixed sample square investigating in successive years at the edge of the oasis in Minqin,Gansu,the impact of precipitation and underground water on the growth and decline of Nitraria tangutorum community was studied.The result showed that the desiccated environment in oases driven by the decline of underground water level was favorable for the growth and develoment of N.tangutorum community,and made this species more xerophilous.This declining underground water level was not a limiting factor for N.tangutorum growth in late years.These N.tangutorum-dominated communities were predicted to survive comparatively longer,and to function as sand fixer and wind breaker at oasis edge in Minqin.When average annual precipitation was about 110mm, N.tangutorum would maintain its normal growth,but the community couldn't spread freely.Only when the annual precipitation was up 140mm in two years running,could its growth be improved.