Abstract: Under the background of carbon neutrality, the demand and usage of lithium (Li) continue to increase, and the pollution of Li in the environment has become one of the emerging environmental issues of global concern. Sansha bay is the largest bay in Fujian Province, with well-developed marine aquaculture. In recent years, lithium battery new energy, new energy vehicles and other industries have developed rapidly around the Sansha bay. There is a risk of discharge or leakage of Li containing wastewater, which poses certain environmental pressure on the marine aquatic ecology and aquatic product safety. In view of this, the monitoring of Li concentration in surface seawater and sediment in Sansha bay were carried out, and the spatial distribution pattern and potential influencing factors of Li in summer seawater and sediment were then identified in this study. The results showed that the concentration of Li in the surface seawater ranged from 129.7 µg/L to 178.4 µg/L, and the Li content in sediment ranged from 24.4 µg/g to 60.2 µg/g, which is at a moderate level compared to other regions. The spatial distribution of Li in the seawater showed a trend of low value near the coast and high at the bay mouth. It was suggested that source of Li is different from nitrogen and phosphorus and its distribution is mainly controlled by the salinity of seawater. There is a significant variability in Li content in sediments, inferring that the substrate types and hydrodynamic conditions would promote the enrichment of Li input from terrestrial sources in sediments. Li pollution in nearshore sediments requires attention in Sansha bay.