In this paper, the 60-MeV proton beam is used to carry out the proton irradiation experiment on NAND (not and) flash memory, the single-event-upset cross section data of the floating gate cell are obtained, the annealing rule of the floating gate cell errors is analyzed, and the effect of proton irradiation on the data retention capability of floating gate cells is studied. The obtained results are as follows. The single-event-upset cross section of the floating gate cell increases with the increase of proton energy, and decreases with the increase of proton fluence. The floating gate cell errors continue to increase over time, and this effect is more pronounced when low energy protons are incident. After proton irradiation, the data retention capability of the floating gate cell is significantly degraded. The analysis suggests that the high energy protons are indirectly ionized through the nuclear reaction with the target atom, causing single-event-upset of the floating gate cell. The correlation between the upset cross section and the proton fluence is due to the difference in single-event-effect sensitivity of the floating gate cell. The proton-induced non-ionizing damage can form partially permanent defect damage in the tunnel oxide layer, creating multiple auxiliary trap channels that can leak floating gate electrons, resulting in the increase of floating gate cell errors and the degradation of data retention capability.