Abstract: The actuator output energy chart is plotted by analytic solution for a simple SEA (with a elastic component) model, and the energy amplification characteristics of the simple SEA model are analyzed, therefor, the issue of no analytic solution in Paluska's SEA energy analysis is solved. In addition, for the over-simplification of the dynamics model in Paluska's analysis, the equivalent mass of transmission mechanism is introduced to improve the energy amplification model of SEA. The parameters of the SEA energy amplification model are normalized to simplify the solution and analysis. Furthermore the numerical solution is calculated under the normalized condition using frequency domain transformation, and the output energy chart of the actuator is plotted. Thereby the SEA energy amplification characteristics of the proposed model are obtained, and its variations with the system parameters (stiffness of the spring, equivalent mass of the transmission mechanism) are obtained.