Oscillation energy analysis is a new method for low frequency oscillation analysis.The relationship between oscillation energy analysis and eigenvalue analysis is studied.The energy flow in the generator is clarified.The oscillation energy dissipation is then computed based on the results of eigenvalue analysis，and the energy dissipation coefficient of a generator is defined.The real part of the eigenvalue of an oscillation mode is negatively proportional to the sum of energy dissipation coefficients of all generators.The real part of the eigenvalue and the total energy dissipation are opposite in sign， and the damping ratio of the system comes from the energy dissipation of each generator.In a one-machine infinite-bus system， the energy dissipation coefficient is equal to the damping torque coefficient.In a multi-machine system，the energy dissipation coefficients can be used for quantitative assessment of generator damping.The conclusions are verified by simulation results， laying a solid foundation for the oscillation energy analysis method.