Abstract: The maximum entropy is used to generate the maximum entropy probability density function(MEPDF) of dam monitoring data,based on which the calculation method of dam safety monitoring index is provided.The MEPDF is concluded just from the digital eigenvalues of the dam monitoring data,not from the assumption of classical probability distribution,which includes the least subjective assumptions.Combined with engineering project,the efficacy and feasibility of MEPDF are proved based on the comparative analysis with the traditional method.