Abstract: The deviations exist in dam safe monitoring data inevitably. Whether it is reasonable has a significant impact on the accuracy of analysis and diagnosis of dam safety situation. On the basis of data characteristics analysis， the multiple-source information fusion technology is introduced to construct a 3-level analysis model of information rationality that is from numerical-fusion to characteristics-fusion and then to decision-fusion. Then typical methods of each level are given, and from which the system structure is made up for dam safety monitoring data rationality analysis in this study.