Abstract: The process of construction and the quality of concrete materials can lead to the randomness of arch dam materials.To evaluate the influence of the randomness of dam concrete materials on the seismic performance of arch dams under strong ground motions, taking the Baihetan high arch dam as a case, we investigate the relation among the relevant length that represents material heterogeneity, the mean value of material parameters and the failure of arch dams.The endurance time analysis(ETA) is used to generate the artificial ground motion time history.It is assumed that the dam material parameter value follows the uniform distribution within a specific interval.At the same time considering the local continuity of the dam material, the correlation length is introduced into the uniform distribution formula.Based on covariance matrix decomposition and center point discretization technology, we establish a finite element model of the arch dam random field corresponding to different correlation lengths.And its dynamic response under the ground motion is analyzed.The relative displacement, transverse joint opening and damage volume ratio are selected as the damage evaluation indexes.The time-varying probability density curves of each index are calculated based on the probability density evolution method(PDEM) and the direct probability integration method(DPIM),and the failure probability curves of different indexes are calculated to evaluate the failure probability of the dam body under different peak ground acceleration(PGA).The analysis results show that after considering the randomness of the dam material, the dam damage distribution is scattered, and the analysis results under different conditions are more discrete.The damage is mainly affected by the correlation length and the mean value of material parameters.The longer the correlation length is, the better the seismic performance of the dam body is.