In order to get the water information quickly in arid and semi-arid areas, Chaoyang City of Liaoning Province was taken as a study area. The soil humidity information was acquired by taking use of MNDWI and based on TM multi-spectral data. The soil humidity information classification map was made by classify the soil information with vegetation, rock and surface water being processed. At the same time, in order to compare the groundwater information of the area with higher soil humidity, investigation was executed to compare the the hydrological and geological data. The basic conclusion was consistent with the remote sensing, so as to prove that this method is feasibility and validity in arid and semi-arid areas.