Abstract: Taken Gaoyou Lake as the study area, and Thematic Mapper(TM)imagery as data sources, field investigation data, single-band threshold method, spectral relationship method, and water indices of simple ratio, Normalized Difference Water Index(NDWI), Modified Normalized Difference Water Index(MNDWI)and Combined Index of NDVI and MIR for Water Body Identification(CIWI)were applied respectively to extract information of water body. The results of information extraction by use of the six methods were compared to determine the optimal method for water body extraction. The results showed that spectral relationship method was easy to eliminate classification errors caused by shadows from the built-up while CIWI water index was easy to eliminate classification errors caused by built-up. Therefore, the combination of spectral relationship method and CIWI water index could achieve a higher accuracy of water body extraction effectively. The combination method presented in this study could reduce the misclassification and increase the accuracy of extraction of water body. The overall extraction accuracy of water bodies was 95.2% and the commission rate was 4%, which suggested that the combination method was a simple and effective method with relatively high precision.