Abstract: Tandem accelerator can generate MeV-level positive ion beam, of which He ion beam can be used for experimental research and industrial applications such as ion beam analysis and ion implantation, which is an indispensable ion beam for tandem accelerator. Tandem accelerator requires negative ion injection, and the negative helium ion beam is the key to generate MeV-level He ion beam for tandem accelerator. Due to the fact that the electron affinity energy of the ground state He atom is less than 0, it is not possible to generate and extract He⁻ ion beam directly from the ion source, but only through the process of two consecutive charge exchanges, so He⁻ ion beam is considered to be one of the most difficult negative ion beams to generate. For the injection need of He⁻ ion in tandem accelerator, a negative helium ion source was designed, in which He⁺ ion beam was generated by using a multi-cusp magnetic field ion source, and then injected into a charge exchange cell, where negative helium ion beam was generated by charge exchange. The magnetic field configuration and particle trajectory of the multi-cusp magnetic field ion source were simulated, and the multi-cusp magnetic field configuration on electron confinement was verified to be able to maintain the ion source discharging stably. The structure of charge exchange cell was designed, the temperature distribution at the thermal equilibrium state was considered, and the long-term stable operation of metal Cs as the charge exchange medium was ensured. Based on the low-energy beam line platform of the 1.7 MV tandem accelerator of China Institute of Atomic Energy (CIAE), experiments on the generation of negative helium ion beam were carried out. The focusing and transport parameters of the ion beam were optimized, and the effects of the charge exchange cell operating temperature and the injection energy of He⁺ ion on the He⁻ ion yield were measured. The maximum He⁻ ion yield was measured to be (1.76±0.03)%, and the maximum He⁻ ion beam of 1.5 µA was obtained by adjusting the discharge parameters of the ion source, which basically meets the injection requirements of the tandem accelerator. Further improvement of the ion source in the future will enhance the discharge intensity and increase the extracted He⁺ ion current intensity, which is expected to further enhance the He⁻ ion current intensity. This research provides important technical support for the development of domestic negative helium ion source, and is of great significance for realizing the independent control of tandem accelerator technology.