The basic method to establish a mathematical model of bending vibration of Euler beam using Lagrangian bond graph is studied in this paper.Out of the request for the generalized coordinates from energy transformation matrix in Lagrangian bond graph method,Euler beam will be discretized into a rigid bar-massspring model.Only generalized deflection variable is defined.And the mathematical model of bending vibration is deduced under various boundary conditions.Simulation on a beam with both ends simply pivoted is carried out,and the results are compared with the theoretical analysis and the results of finite element method,which proves that the discrete model of the beam is effective and accurate,and modeling by use of Lagrangian bond graph is feasible.