Abstract: We applied high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to analyze the composition and concentrations of liposoluble algal toxins accumulated in Crassostrea rivularis which were sampled in April 2017 (spring), July 2017 (summer), October 2017 (autumn) and January 2018 (winter), respectively. The homo-yessotoxin (homo-YTX), gymnodimines (GYM), spirolide1 (SPX1), azaspiracid2 (AZA2) and pectenotoxin2 (PTX2) were detected and their concentrations varied with sampling season. The concentration of GYM was the highest with a maximum of 13.15 μg·kg⁻¹ in winter, while the others were low (0.54–1.40 μg·kg⁻¹). With risk entropy method and evaluation method to safety risk assessment, it is shown that the RQ value and exposure risk index are far below the limits. Therefore, these samples are safe for consumers.