As city's matrix landscape，impervious surface dominates urban landscape patterns and processes.It is not only a typical characteristic of urban surface cover

but also one of the main factors in the change of urban environment.This paper uses Landsat ETM+ satellite images to detect three-phase impervious surface information of the Kunming City from 2000 to 2010.We extract water information by using modified normalized difference water index and exclude the impacts of water on impervious surface extraction accuracy.Based on the negative correlation between urban impervious surface and vegetation coverage

we extract impervious surface information of the study area and obtain higher extraction accuracy.This study can better reflect the trend of urban expansion and the damage extent to the periurban ecological environment.Results from the study showed that impervious surface area of the study area increased so fast in the last ten years.The city is continuing to expand to the suburbs

which has a great impact on the surrounding ecological environment and result in a serious decline in the suburban vegetation cover.