Abstract: Theoretically and practically, fire is possible to break out aboard a manned spacecraft. Therefore, the fire safety for mannedspacecraft is an important part of microgravity combustion research. Theoxygen concentration and gas velocity have a significant effect on theflammability of solid materials. For both counter-flow and concurrent-flowflame spreading over solid materials, the flammability has a limit determined by oxygenconcentration and gas velocity, i.e., it is a blow-off extinction at high gasvelocity, but a quenching extinction at low gas velocity. The limit oxygen concentrationand the limit gas velocity are critical index to evaluate the flammability ofmaterials. Under microgravity, the possibility of occurring both flamingcombustion and smoldering is increased in a low speed flow. Consequently,eliminating the potential fuel in materials used in spacecraft is the mainmeasure for fire prevention. However, materials used for a spacecraftthat can resist combustion are very few. To ensure fire safety, thefire detection and the fire fightingmethod are necessary. There are similarities and differences between thefire safety projects in America and Russia. At present, there are still manyproblems to be resolved for the fire safety for manned spacecraft.Considering the actual condition of our country, the present author thinksthat the simulation under the normal condition of the microgravity combustioncharacteristics of materials using both experimental and numerical methods ispractical and important for fire safety of our country's manned spacecraft.