Abstract: The neutron-induced single event effect affects the reliability of electronic devices used in aircraft and ground nuclear facilities. With the progress of semiconductor technology, device feature sizes become smaller and more integrated, radiation sensitivity increases and neutron single event effects become more of an emphasis. To evaluate the performance of electronic devices against neutron single event effects, ground-based neutron irradiation experiments are the most commonly used method in China and abroad. The quasi-monoenergetic neutron is an important neutron source for studying the law and mechanism of the neutron single event effects. Meanwhile, through irradiation experiments with multi-energy neutron beam, the energy dependence curve of the neutron single event effect cross section can be obtained, which can be used to predict the error rate of electronic devices exposed to various neutron radiation environments. Systematic experimental studies of the energy dependence of the neutron single event effect cross section have not been carried out in China, mainly due to the fact that there are few neutron sources suitable for conducting neutron single event effect experiments in China, especially the long-term lack of quasi-monoenergetic neutron sources above 20 MeV. In recent years, with the gradual completion and commissioning of several medium- and high-energy proton accelerators in China, quasi-monoenergetic neutron experimental research has become increasingly available. Theoretical simulation studies prior to the implementation of experimental studies. Based on the nuclear reaction theory, the secondary neutron yield and the neutron single energy peak yield were studied with 50-500 MeV proton and lithium bombardment. The trend of lithium target thickness was calculated by SRIM software with 1.3 MeV proton energy loss in lithium target. The thickness of lithium target with proton energy loss of 2 MeV, secondary neutron yield and neutron energy spectrum in different emission directions were simulated by Monte Carlo method for 50-500 MeV proton. The simulation results show that quasi-monoenergetic neutrons in 0° direction have the best monochromaticity, the neutron fluence rate can reach 10⁴-10⁵ cm^-2·s^-1 and the proportion of single energy peak is about 50%, for the position of 5 m from the Li target, when the proton intensity is 1 μA and the target thickness is 2 MeV proton energy loss, which can meet the research requirements of neutron single event effect. In conclusion, this work provides theoretical guidance for the design of quasi-monoenergetic neutron targets, beamlines and experimental terminals for neutron single event effect experiments, as well as for the implementation of neutron single event effect irradiation experiments.