Abstract: The current researches on shale gas formation damage derive from the conventional theory of sandstone reservoir and carbonate rock reservoir. To review the researches of shale gas formation damage, factors affecting penetration ability were focused on. It was thought that the internal factors have mainly been recognized as listed below: the low-permeability leads to water block; the high content of clay tends to swell and block channels; shale surface capillary force increases resistance to gas flow; the conditions of high temperature and high pressure do harm to the performance of working fluids and easy to increase the reservoir fluids residual; the CO2 flow contaminates the working fluids and increases the residual. While the external factors of formation damage include the following items: the swell of clays caused by the insufficient inhibition ability of working fluids; the invasion and residual of working fluids as well as the additives; the biofilms generated by working fluids obstruct gas flow in reservoir; and the liquid volatilization speed around the borehole is too low to prevent water blocking and causes channel blocking, which results from low production pressure. The mechanisms of the formation damage during desorption and diffusion process in shale gas has not been systematically researched as well as the effects of different processes such as drilling and completing, reservoir stimulation and drainage on desorption and diffusion capacity. The basic theory on the formation damage of the shale gas has not been established. Moreover, there is no agreed evaluation criterion on shale gas formation damage indoor and in the field on shale gas.