Abstract: The hybrid pencil beam model (HPBM) is an effective algorithm for calculating electron dose distribution in radiotherapy. The mean energy distribution of incident electron beam in phantom is one of the factors that affect the calculation accuracy of HPBM, especially in field edge areas near the end of the electron range. A new fitted formula based on Monte Carlo (MC) simulation data for electron beams with energy range of 6-20MeV in the homogeneous water phantom is proposed in this paper. The precision of the fitted formula within the scope of the energy was evaluated by comparing the electron dose distribution of ECWG measured data with that obtained from HPBM which took the mean electron energy that calculated by the fitted formula and the existed empirical formula, respectively. The results showed that the accuracy of dose distribution that obtained by the mean electron energy calculated with the fitted formula increased about 1%.