Remote sensing is an important technology in the field of drought monitoring. Most traditional methods by remote sensing construct relationship between image features and land real data. Usually the models are complicated and the parameters are difficult to confirm. The surface water directly influence the irrigation and drinking, so monitoring water area changing can reflect drought situation. In this paper, Henan province in China is an example to construct monitoring model. By water body extraction and water area calculation from GF-1 and Landsat8 satellites in the drought and normal period, the relative deviation of water area is achieved to march drought grade according to soil moisture. The method is more simple and direct, and can supplement traditional methods to monitor drought.