The failure of concrete dam is a process started from local failure to global instability, and there is a huge scale difference in the process, so the analysis should be conducted in a multiscale manner. Choosing a typical failure curve as a signal, the precursor load is determined in the form of singularity point in the curve. With a numerical example, the previous reported methods for determining precursor load are compared with the wavelet approach, and it is shown that the wavelet approach gives more accuracy and reasonable results. Besides the precursor load, the failure mode, local failure or global instability, can also be figured out by the wavelet approach. By applying it to the Jinping arch dam, the obtained results are in good consistency with geology mechanical test. It is shown that the wavelet approach is of good applicability and accuracy for dam failure analysis.