For the flaw of safety evaluation system using safety factor as control index, seismic permanent deformation is used to evaluate the safety of earth rock fill dam. In this study, the seismic deformation of Zipingpu dam after Wenchuan earthquake is measured and analysis. The deformation in the middle of the riverbed on the crest is the largest. The deformation in the left dam abutment is smaller than that in the right. The seismic permanent deformation on the crest grows rapidly in the first three days, and then develops slowly. The results show that deformation grows along the height of dam with the relation of exponential or power function.