Data fusion of SAR (during flood event) and LANDSAT TM (before flood event) has been well known to detect flood disaster, owing to that the all-weather and all-time ability of microwave remote sensing and the abundant information and good interpretation of TM. In this paper, firstly, an approach named TIN (Triangulated Irregular Network) was used for registration, with better accuracy than other general methods. Secondly, according to statistic analysis including interband correlation and entropy, etc. the selection of the optimal bands of TM was discussed. In order to monitor flood event better and more quickly in future, we analyzed various fusion approaches to see which is optimal and less time-consuming with the data of 98's flood happened to the Yangtze River. As a result, the pseudocolor image of composition of TM5-SAR-TM3 is the best, however, the combinations of TM5-SAR-TM2, TM7-SAR-TM2 and TM7-SAR-TM3 are also alternative and feasible.