This paper presents to verify the energy harvesting of a nonlinear piezoelectric multilayer beam under harmonic excitation. In this paper, a numerical program is developed with Matlab software. In the program, the Newmark technique for dynamic analysis is used, and the Newton-Raphson iterative and Simpson methods are used for the nonlinear solution. Numerical approximation of the nonlinear equations uses a mixed finite element formulation in terms of displacement and potential electrical variables. To verify the numerical results, the experimental results for the energy harvesting of a piezoelectric multilayer beam with harmonic base excitation are used. The multilayer piezoelectric beam used consists of two bimorphs in the case of a series connection and a substructure layer of aluminum. For the considered electrical circuit, the piezoelectric energy harvesting model is connected to the resistive load and the generated power in multilayer piezoelectric beam is sent to load resistance. The influence of the type of layer connection on the output voltage value is investigated. The generated voltage and electrical power of the resistive load are verified using a ‘31’ mode piezoelectric multilayer beam in both resonance and off-resonance cases. The effect of the energy loss factor, resistive load, and excitation frequency on the results of the power and voltage generated are studied.