Four types of NOR Flash memories from different manufacturers with 90 nm feature sizes are studied, based on the HI-13 accelerator of the China Academy of Atomic Energy. Aiming to evaluate the Single Event Upset(SEU) effect for those memories, heavy-ion with different Linear Energy Transfer (LET) values is utilized to irradiate the devices. Both static and dynamic tests are performed to obtain the SEU cross-section of the device. Test results show that the memory with large capacities has a slightly bigger SEU cross-section than the devices with small capacities. There is almost no impact on the SEU cross-section of the device with or without bias. The SEU cross-section of the domestic alternative devices is bigger than that of two foreign commercial devices. The LET threshold of the domestic alternative devices is nearly at 12.9 MeV·cm2/mg, while that value of foreign commercial devices between 12.9~32.5 MeV·cm2/mg. The SEU cross-section results from static and dynamic tests have good consistency, which indicates test mode has no obvious influence on SEU effect. In addition, the synergistic effects of Single Event Effect(SEE) and Total Ionizing Dose(TID) effect for Flash memory are also studied, the results show that TID dose will increase the sensitivity of the device to SEE. The analysis shows that the ionization caused by the TID effect leads to the electron leakage from the floating gate and the drift of transistor threshold voltage, therefore SEU is more likely to occur on the basis of TID effect.