Abstract: Zhanjiang bay is a semi-enclosed bay with a very narrow entrance. Previous studies have shown that the Zhanjiang bay is at the stage of medium-phosphorus-limited potential eutrophication. Phosphorus release from sediment can increase the risk of water eutrophication. Inorganic phosphorus (IP), organic phosphorus (OP) and total phosphorus (TP) were measured in the surface sediments of Zhanjiang bay in spring and summer. The spatial-seasonal variations of these phosphorus forms and their influencing factors were studied. This study can provide scientific basis and data support for environmental protection of Zhanjiang bay. The main results were listed as follows. In spring, the average concentrations of IP, OP and TP were 236.2 μg/g, 111.3 μg/g and 347.5 μg/g, respectively. In summer, the average concentrations of IP, OP and TP were 168.8 μg/g, 92.4 μg/g and 261.2 μg/g, respectively. The concentrations of these three phosphorus forms were high in spring and low in summer. In both spring and summer, the concentrations of IP, OP and TP were highest in the channel of Zhanjiang bay, intermediate in the coastal area of Zhanjiang bay, and lowest in the central Zhanjiang bay. The percentages of IP in TP were relatively high in the coastal and central area of Zhanjiang bay. The percentages of OP in TP were relatively high in the channel of Zhanjiang bay. Different forms of phosphorus in surface sediments of Zhanjiang bay had obvious spatial and seasonal variations. Organic matter decomposition, terrestrial inputs, sewage inputs, mariculture activities, grain size compositions of sediment and hydrodynamic conditions were responsible for the spatial and seasonal variations of phosphorus forms in the surface sediments of Zhanjiang bay.