Abstract: Effects of cold shock on 8 biochemical and 6 cellular immunological parameters were detected in Litopenaeus vannamei by biochemical analysis and flow cytometry to investigate the cold tolerance of this species. The results showed that， when water temperature decreased from 30℃ to 16℃ with a decreasing rate of 4℃/h， serum glucose significantly decreased， other biochemical parameters in serum including total protein（TP） ， alanine aminotransferase （AST） ， alanine aminotransferase（ALT） ， cholesterol， triglycerides， lactate dehydrogenase（LDH）and creatine kinase（CK）activity/level increased in various degrees. Total haemocyte count（THC） ， reactive oxygen species （ROS）production and non-specific esterase（NSE）activity significantly decreased after cold shock， while apoptotic cell ratio significantly increased. The above results reflected the effects of cold shock on energy metabolism， cellular membrane permeability and celluar immunity of L. vannamei. Cold shock may cause blood serum exhausting， enhance decomposition of protein and lipid， increase cellular membrane permeability and tissue injury， metabolizing enzymes leaking out， and impaire celluar immunity. It can be concluded that L. vannamei is very sensitive to cold shock， which may result in physiological depression of the species.