Abstract: This paper presents an approach to integrating remote sensing inversion and data assimilation to better estimate soil moisture over a large area.In support of the Microsoft.Net and ESRI ArcEngine,the C# and RSI/IDL are used to develop software modules to implement the models for soil moisture estimation from MODIS and AMSR-E data.A software package for soil moisture retrieval and data assimilation is developed by integrating the inversion modules,data assimilation modules and GIS modules.This application offers a tool for soil moisture estimation over a large area using remotely sensed data and proposed models,enabling related management departments to operationally map large-area soil moisture for assessing ecological and environmental quality.