The temperature variation law and mechanism of commercial Flash memory devices applied in space electronic products were analyzed. The temperature cycling test and high temperature step stress test of highly scaled Flash memories K9××G08U×D series of Samsung were carried out at the temperature -35-+105 ℃ to evaluate the feasibility of its space application. The results show that the page programming time and block erasing time of this series of memory changes with the temperature. The page programming time increase by 15% from -35 ℃ to 105 ℃. Block erasing time increase by 72% from normal temperature to -35 ℃. Block erasing time increase by 10% from normal temperature to 105 ℃. The experiment shows K9××G08U×D series memory can work at -35-+105 ℃. Under such environmental temperature condition, the Flash can be read, programmed and erased. No new bad block occurrs. The page program times increase with the temperature increasing and still less than the maximum page program time. In low temperature, the erase times increase dramatically. So in space application enough time should be given for erase operation.