Abstract: Dense phase carbon dioxide (DPCD) is a non-thermal processing technology, which affects microorganisms and enzymes through molecular effects of CO2 under pressures below 50 MPa and 60℃. DPCD has less significance effect on the quality of foods. DPCD has been applied to the process of meats, vegetables, seeds and food powders, fruits, spices and herbs, and fish. The studied objective is to investigate the effects of DPCD on bacteria inactivation and qualities of Haliotis discus hannai and to explore whether it can be applied to process Haliotis discus hannai. In this paper, the effects of pressure (5-25 MPa), exposure time (10-50 min) and temperature (30-50℃) of DPCD treatment on bacteria inactivation and qualities of Haliotis discus hannai were studied. DPCD can reach the ideal sterilizing effect for Haliotis discus hannai under the conditions of pressure 20MPa, temperature 45℃, exposure time 40-50 min. Compared with Haliotis discus hannai cooked in boiling water for 2 min (logarithmic decline of 3.59), the sterilizing effect was the equivalent by DPCD of 20 MPa and 45℃ for 40-50 min (logarithmic decline of 3.46). The total number of colonies was less than 1000 CFU/mL. Compared with untreated Haliotis discus hannai, DPCD treatment had no significant effect on muscle pH value and appearance of Haliotis discus hannai (P>0.05), the reason was that the solubility of CO2 was lower in solid foods. However, DPCD treatment had the significant effects on color, proximate composition, weight loss, water holding capacity and texture (P<0.05) and the effects were more obvious with DPCD treatment parameters increasing, which could be related to protein denaturation. Combined with the bactericidal effect, optimum conditions of Haliotis discus hannai treated by DPCD are: 20 MPa, 45℃, (40-50) min. The results provided the reference for processing shellfish foods by DPCD.