An online solid phase extraction ( online-SPE) combined with ultra high performance liquid chromatography-quadrupole linear ion trap mass spectrometry (UHPLC-MS / MS-Qtrap) was established for the simultaneous identification and determination of 10 kinds of algal toxins in water samples. Multiple injections of water samples were controlled by a preset program, and the target analytes were enriched by trap column. The six-way valve was switched subsequently, and the algal toxins in the trap column were back-flushed to the analytical column for separation and analysis. The results showed that the online SPE significantly simplified pretreatment process, and the linear ion trap tandem mass spectrometry improved the sensitivity of the determination. Moreover, the establishment of enhanced product ion (EPI) scan library provided evidence for the confirmation of algal toxins. The 10 kinds of algal toxins showed a good linear relationship with correlation coefficient R2>0. 99. The limits of detection (LOD) were 0. 0015 -0. 0050 μg / L. The mean recoveries at three spiked levels of 0. 02, 0. 1, 1. 0 μg / L were from 83. 7% to 98. 5% . The method was suitable for the rapid confirmation and quantitative determination of various algal toxins in water.