Abstract: After the disaster, the increase of suspended matter in water and the high water content crops will lead to the low accuracy of conventional methods of water body information extraction. In response to this problem, a new method of extracting flood submerging area for farmland based on tasseled cap transformation is presented in this paper. First, the remote sensing images before and after disaster are pre-processed by radiometric calibration and atmospheric correction. Then, the tasseled cap transformation is performed based on the coefficients corresponding to the sensor to obtain the greenness component and the wetness component. Third, the wetness component is divided by the OTSU method, and combined with the greenness component to obtain the warterbody information. Finally, the spatial overlay analysis of the waterbody information and farmland vector data is carried out to extract the flood submerging area for farmland. Taking Yueyang City of Hunan Province and its vicinity as research area, the accuracy of the proposed method is evaluated both qualitatively and quantitatively to verify the validity and applicability of the method. The results shows that the boundary of flood submerging area for farmland is clear, the range is more accurate, and the producer's accuracy and the user's accuracy are 0.97 and 0.90, respectively. This paper provides references for agricultural risk evaluation and dynamic monitoring of flood disaster.