Abstract: To investigate the content and distribution of aluminum (Al) speciation in Ostrea rivularis, we optimized the extraction conditions for four kinds of chemical reagents by sequential chemical extraction method and inductively coupled plasma mass spectrometry (ICP-MS). The results show that the optimized extraction conditions were 70 mL 0.5 mol·L^–1 KCl extracting for 2 h, 70 mL deionized water extracting for 2 h, 70 mL 4 mol·L^–1 HCl extracting for 2 h, 70 mL HNO₃ extracting for 2 h. Under these conditions, the distribution of aluminum species in the whole O.rivularis followed the order of organic Al<Al³⁺<water soluble Al<Al(OH)₃<insoluble Al. The insoluble Al accounted for about 77.36% in total aluminum, while the dominating form of toxic inorganic aluminum was Al(OH)₃, which accounted for 15.87%. The percentage of dissolve aluminum at gastric stage accounted for 8.16% –32.11% of the total aluminum, which indicates that due to the acidity of gastric juice and the effect of enzyme, the aluminum speciation changed in the gastric juice.