Abstract: Without any charge storage, the Magneto-resistive Random Access Memory (MRAM), as a nonvolatile memory, enjoys a natural advantage of its capability against the space radiation. The working principle and the radiation-hardening mechanism of MARM are analyzed in this paper by taking the type MR0A08BCYS35 as an example, and the heavy ion SEE test is carried out on this kind of MRAM. Based on the test result, the SEU rate of this kind of MRAM under the GEO radiation condition is calculated by the self-developed software Fore CAST^®. Suggestions are then made for the corresponding space applications.