Abstract: With the huge development of space industry, an emerging subject named Space Microbiology is coming with the tide of fashion. Compared with the earth's biosphere, there are some special environmental factors in outer space, such as cosmic radiation, microgravity, space vacuum, low intensity magnetic feld, ultralow temperature, thermal extremes and so on. These conditions of outer space present an environmental challenge for not only astronauts but also bacteria. Vast literatures in the effects and mechanisms of space environment on bacterial responses are reviewed in this article in order to promote the development of Space Microbiology.