Abstract: Hydrogen peroxide (H₂O₂) is a reservoir and sink of free radicals, and also an important oxidant in the tropospheric atmosphere. Research into the literature was conducted to summarize publications about H₂O₂ since 1990s, including the formation route, pollution characteristics and the effect factors. The results showed that H₂O₂ exists in the atmosphere, cloud drops and particles. In the atmosphere, H₂O₂ is generated mainly through photolysis of O₃ and formaldehyde, reactions of VOCs and OH·/O₃, etc. Atmospheric concentrations of H₂O₂ range from nd to 8×10^-9, with high concentrations around noon and low concentrations in the morning and in the evening on clear days. H₂O₂ concentrations increase with the increase of O₃ concentration and the decrease of NO_x and VOCs concentration. The increase of solar radiation and temperature or the decrease of relative humidity causes the increase of H₂O₂ concentration. The reaction in which H₂O₂ oxidizes sulfur dioxide to sulfuric acid is one of the most important reactions in aqueous-phase chemistry, leading to the formation of acid rain and the increase of secondary aerosol concentrations. In addition, the ratio of H₂O₂/HNO₃ indicates the limitation of VOC or NO_x in the O₃ formation. In the future, more work on the measurement of key factors such as OH· concentration and photolysis rate of NO₂ and O₃ that influence H₂O₂ formation should be carried out. More studies on H₂O₂′s contribution to SO₄^2- formation and on the ratio of H₂O₂/HNO₃ as an indicator to ozone-NO_x-VOCs sensitivity in different regions under the special atmospheric environment in China should be carried out as well.