Background：Neutral beam injection is one of the main auxiliary heating methods in controllable nuclear fusion experiment. The positive ion source is adopted in the EAST-NBI （Experimental Advanced Superconducting Tokamak-Neutral Beam Injection） device, and during its operation, there is a large energy deposition on ion source components, especially on the electron dump. According to previous research, when beam power is 3.5 MW, the average power density deposited on electron dump is around 4.4 MW·m2, which may cause great burden for its heat transfer capacity.Purpose：Research on the heat transfer conditions of electron dump is of great significance. Methods：A numerical simulation method is adopted to calculate the heat transfer effect with the change of beam power and inlet pressure of cooling water, and the maximum operating time of electron dump is obtained.Results：The results show that the heat transfer effect decreases with beam power growth, and by enhancing the inlet pressure of cooling watervia booster pump, heat transfer capacity gets better to some extent, which can extend the maximum operating time of electron dump.Conclusion：This research can guide EAST-NBI ion source to operate safely and steadily. Moreover, it can lay a foundation for increasing heat transfer capacityvia structure optimization in future work, which is meaningful for the development of long pulse and high power ion source.