The concentration of copper is extremely low in the surface water of the open ocean. Copper has multiple speciations and the dual functions of bioavailability and toxicity. Copper in seawater can regulate phytoplankton and affect the primary production， playing an important role in marine biogeochemical cycles. With the advancement of sample collection and analysis techniques， the biogeochemical research of copper in seawater has developed rapidly in the past 30 years. Here， we provide a comprehensive review on marine copper biogeochemistry. Firstly， we summarized the physiological and ecological effects of copper on phytoplankton and microorganism. For example， copper can participate in the life processes of phytoplankton and microorganism， interact with other metals and have the toxicity. Secondly， we reviewed the chemical forms of copper in seawater （such as valence states， speciations， complexation with organic ligands and bioavailability）. Finally， we summarized the sources and sinks of copper in the ocean （and the fluxes and isotopic composition）， the horizontal and vertical distribution of copper in seawater， and factors influencing these were also reviewed. We suggest future research topics dealing with copper biogeochemistry to provide new insights into the role of copper in seawater and biological cycles.