Organic metal-binding ligands represent an essential role in the bioavailability of trace elements since they govern the species and sizes of those elements in seawater. The distribution and properties of organic ligands in seawater as well as the factors influencing their complexation abilities were summarized in this paper. Most organic ligands exist in the low molecular weight fraction, and their concentration nearshore is often higher than that of open ocean while the vertical distribution varies in different areas. The complexation of trace elements and organic ligands is influenced by several factors such as molecular weight of organic ligands, salinity, pH, biological activities and redox conditions. Ligand with a lower molecular weight usually represents stronger complexation ability, whereas the opposite seems to be true sometimes due to the specific affinity between some elements and ligands. Increasing salinity lowers the electrostatic repulsion among adjacent functional groups of ligands and thus decreases their complexing rate, yet increasing pH promotes the ionization of organic ligands and results in the formation of more complexes. The utilization of phytoplankton and degradation of microorganism release more low molecular weight organic ligands while more high molecular weight ligands are released from marine organisms under heavy metal stress. Therefore, sufficient significance should be attached to characterizing the structure and molecular weight of organic ligands and exploring the interaction between trace elements and organic ligands and the influence of related marine factors on their behaviors, which will certainly help us to understand the global biogeochemical cycles and ecological significance of trace elements.