The human exploration of space is one of the great voyages of discovery in human history. For over forty years space exploration, human have gotten more profound knowledge about outer space and life phenomena, ranging from understanding and recognizing space to adapting and utilizing space. With these development, space medicine that aimed at studying effect of space environment on human health and ensuring the safety, health and effective working of human in space exploration, will become increasingly improved and matured.The contents of research will develop from the early phenomena observation of the effect of space environment on human physiology and biochemistry, and the effect definition, to the study of the mechanism of changes of cell, molecule, and gene, from the passive adaptation for space environment to taking the initiative countermeasures, in order to ensure the safety, health and effective working of astronauts during space flight.Space practices in the past forty years have confirmed that a variety of physiological and pathological changes have been found for organism exposed to space flight. These changes include cardiovascular dysfunction, bone loss,muscle atrophy, decline of immune function, endocrine function disorder and space motion sickness. In recent years, more attention has been focused on the study of the mechanism of these changes, especially the effects of space environment on cell, molecule and its gene expression. With the demand of China's manned space engineering task and continuous development, a series of studies on medical problem caused by space environment have been carried out.