The combined effects of CO2 and cold seawater on the quality of Pacific white shrimp (Penaeus vanmamei) during the storage were investigated. The results showed that the total bacterial count (TBC), Escherichia coli count, H2S producing bacteria count and psychrophilic bacteria count of shrimp preserved in CO2-cold seawater (4℃) were lower than that of control group (samples were not in CO2-cold seawater but cold stroge). As a result, total volatile basic nitrogen (TVB-N), pH value and K value increased more slowly than that of control during storage. Shrimp in CO2-cold seawater was second-grade freshness (TVB-N value of 19.5mg/(100g), K value of 20.3%) after storage eight days comparing to serious spoilage of control. The shear force of shrimp flesh decreased slowly during storage, but there was no obvious difference. Activity of polyphenol-oxidase (PPO) was significantly inhibited by CO2-cold seawater. Meanwhile, melanosis of shrimp and deterioration of sense quality was delayed.