Hydrogen peroxide can oxidize or reduce a number of biological important trance metals in seawater. Therefore, it can indirectly affect the marine ecosystem by causing the changes in the speciation of these metals. The results of researches about hydrogen peroxide in seawater in the last more than thirty years were reviewed and the direction of study in the further was proposed in this paper. Hydrogen peroxide can be found rather ubiquitously in the upper water at concentration of 0~102 nmol/L. In water column the maximum of the concentrations of hydrogen peroxide presents in surface water and the concentrations decrease with the increase of depth. In general, the concentrations in costal seawater are higher than these in the oligotrophic ocean. Diel variation of hydrogen peroxide occurs in seawater: the concentrations increase since sunup until the mixmum of afternoon and decrease until the minimum at drawn. The sources of hydrogen peroxide in marine environment include photochemical production, atmospheric deposition and biological production, and the photochemical production is primary among them. The sinks of hydrogen peroxide in the ocean consist of biological and chemical and photochemical decomposition and the main one is biological decomposition. The biogeochemistry of hydrogen peroxide in the continental shelf influenced by river water and factors affecting photochemical production and detail of decomposition should be studied in the future.