Abstract: Babylonia areolate is vulnerable to hypoxic stress during aquaculture and transportation. To evaluate the effects of hypoxia stress on its metabolism and immune function, we measured the oxygen consumption rate and ammonia excretion rate of juveniles, and analyzed the gene expression levels of lactate dehydrogenase (LDH), pyruvate kinase (PK), superoxide dismutase (SOD), acid phosphatase (ACP) and alkaline phosphatase (AKP) after the dissolved oxygen (DO) concentration decreased to 6, 4, 2, 1and 0.5 mg·L⁻¹, respectively. The results show that with the decline of DO level, the oxygen consumption rate of B. areolate decreased significantly (p<0.05), and the ammonia excretion rate first significantly increased and then significantly decreased (p<0.05). LDH activity was significantly lower than that of the control group (p<0.05), but significantly higher at 1 mg·L⁻¹ (p<0.05); PK activity was significantly lower than that of the control group (p<0.05), but significantly higher at 0.5 mg·L⁻¹ (p<0.05); SOD activity was significantly lower than that of the control group (p<0.05); the activities of ACP and AKP were significantly lower and then increased, and significantly higher than the control at 1 and 0.5 mg·L⁻¹, respectively (p<0.05). Compared with the control group, the expression level of LDH gene decreased significantly (p<0.05) after the DO level decreased to 4 mg·L⁻¹, and that of PK gene increased significantly (p<0.05) after the DO level decreased to 1 mg·L⁻¹; the SOD gene expression was significantly down-regulated (p<0.05) after the DO level decreased to 0.5 mg·L⁻¹; the ACP and AKP gene expression was significantly down-regulated (p<0.05). The results indicate that B. areolate can respond to hypoxic stress by decreasing metabolic rate and regulating metabolism, immune enzyme activity and gene expression.