Applying the methods of on-site observation and dynamic model, the research on the fronts at Jiulongjiang estuary has been carried out, during which spatial and temporal distribution, dynamic characteristics and formation mechanism of salinity fronts is analyzed and discussed. The research shows that the estuarine fronts mainly lie in the area from Jiyu Islet to Haimen Island, outside of Yuweizai to Hulishan cross section, the near coast of Yuweizai and the south of Songyu-gulangyu channel. The front in the former two regions are formed directly by plume, while the one near the coast of Yuweizai is a tidal intrusion front caused by flood current and the one at the south of Songyu-gulangyu channel is result of current shear transformation. Under normal circumstances, fresh water of Jiulongjiang river mainly influence the inside of Xiamen Bay, and when it is in typhoon seasons, plume front can affect Taiwan Strait and has an effect on the biogeochemical processes in the strait.