Abstract: The exchanges of NO_X between snow and air have a significant impact on the atmospheric components and photochemical processes in the overlying boundary layer, which increases the oxidizing capacity of the atmosphere and may have a decisive impact on the air signals that are retrieved from ice cores. In the recent years, sunlit snow and ice has been proved to be an important NO_X source in the polar boundary layer. This paper makes a thorough review on the release of NO_X from snow and ice, including the following aspects: field observations and experimental evidences, release mechanisms and influential parameters that affect such a release process, polar NO_X concentrations and fluxes, and environmental impacts of the chemical processes of NO_X in the polar atmospheric boundary layer. In the Tibetan Plateau lying in the mid-latitude of Northern Hemisphere, the released NO_X observed recently in the sunlit snow/ice-cover is 1-order magnitude more than that in polar regions, but more in-depth scientific research is still needed to reveal its impact on the atmospheric oxidizing capacity.