Abstract: The high salt in seawater samples brings great challenges for analyzing trace heavy metals. To achieve the green separation and rapid detection of trace lead and copper in seawater, a method of coconut shell biochar enrichment was established. By using the method of adsorption and desorption, lead and copper elements in seawater were enriched on coconut shell biochar, and the coconut shell biochar powder was repeatedly washed with pure water to remove the salt matrix in seawater. The desorption was dissolved with 7.5% HNO₃, and the desorption solution was filtered with 0.45μm filter membranes and analyzed by ICP-MS. Two metal elements showed good linear relationships within the range of 0.10−100μg/L, and the linear correlation coefficients were greater than 0.9995. The method had a detection limit of 0.005μg/L for Pb and 0.006μg/L for Cu, meeting the evaluation requirements of seawater quality assessment stipulated in Technical Specification for Assessment of Sea Water, Marine Sediment and Marine Biological Quality (HJ1300—2023). The spiked recovery rates for seawater samples were between 96.1% and 102.3%, with the relative standard deviation less than 5%. This method had the advantages of simple operation, low costs, environmental protection, and high reliability and sensitivity.