Rare earth elements (REEs) with systematically varying properties are useful indicators of marine geochemistry. However, the accurate determination of REEs in seawater is complicated because of their low elemental concentrations, highly saline matrices, and contamination of the samples during pretreatment. Herein, we report a rapid, automated, and reliable method using a novel automated separation system (ELSPE-2 Precon) that efficiently separates seawater matrix elements and elutes preconcentrated targets directly into inductively coupled plasma-mass spectrometry (ICP-MS) online detection. The detection limits (3 s) were in the range from 0.002 (Dy) to 0.097 ng L-1 (La), and the accuracy of this method was confirmed using a seawater certified reference material (NASS-6). This method was used for the long-term measurement of REEs in three new seawater reference materials (NASS-7, CASS-6, and NMIJ 7204-A) and the preferred values were provided for subsequent studies. Compared with other commercially available systems (i.e., SeaFAST?), the proposed system exhibited a higher throughput (>14 samples/h) and lower sample consumption (< 1 mL/sample).