To evaluate the quality of ecoenvironment in Shaanxi water source area in the middle route of the south??to??north water transfer project objectively can provide the decision??making and reference for the implementation of the project . Under the guidance of ecological system theory and by using remote sensing techniques and the analysis methods of geographic information systems

the paper extracts six factor layer data affecting environmental quality in the study area

then stacks them to be the integrated environmental index layer data

and finally divides it into four environment divisions. From the result of spatial statistical analysis

the first and the second integrated natural indexes are the best

account ing for 64. 69 percent of the total water area; the third is better

accounting for 31. 52 percent ; and the forth is poor

accounting for 3. 79 percent. To evaluate and study the eco-environmental quality in Shaanxi Province comprehensively can provide a data support and a decision??making basis for ecological compensation and soil and water conservation in the middle route of the south??to??morth water transfer project.