Abstract: Dense phase carbon dioxide (DPCD), also known as high pressure carbon dioxide (HPCD), is a promising non-thermal food processing technology. DPCD was originally applied to inactivate microorganisms and enzymes in food. However, many researchers found that DPCD could induce some proteins associated with microorganism metabolism inactivation and the change of the secondary structure of enzyme protein when the food was treated by DPCD. Meanwhile, they also found that DPCD could induce some food protein inactivation. DPCD could not only improve the functional properties of protein but also induce protein to form gel. Our previous study results showed that DPCD could induce shrimp surimi to form gel and the microstructure and texture of gel were better than those induced by heat. Myosin is the key protein of forming gel for animal meat. Protein concentration is an important factor affecting myosin to form gel. Generally, the higher the protein concentration, the greater the ability of forming gel, and the better the texture of gel was. In order to clarify the mechanism of shrimp surimi forming gel induced by DPCD, we used myosin from Litopenaeus vannamei as the subject and researched the effects of DPCD treatment pressure, temperature and time on the least gelation concentration of myosin forming gel and gel strength of shrimp surimi. Firstly, myosin was extracted using the method of reference and the myosin solution with the concentration of 1-14 mg/mL was treated by DPCD, and the least gelation concentration of myosin forming gel was determined. Secondly, shrimp surimi gel was prepared by DPCD and the gel strength was determined using a TMS-PRO texture instrument. The study results were showed as follows: Treatment pressure and temperature of DPCD had a significant effect on the least gelation concentration of myosin forming gel. Though treatment time of DPCD had no significant effect on the least gelation concentration, myosin could form the firm gel by extending treatment time. The least gelation concentration of myosin forming gel was 14 mg/mL at 40 ℃ under the pressure of 5-30 MPa, 12 mg/mL at 50 ℃ under 5-10 MPa, 11 mg/mL at 50 ℃ under 15-30 MPa, and 10 mg/mL at 60 ℃ under 5-30 MPa. Treatment pressure and temperature of DPCD had a significant effect on gel strength of shrimp surimi (P<0.05), and gel strength of shrimp surimi increased with the treatment pressure and temperature increasing (P<0.05). The gel strength of shrimp surimi induced by DPCD was (14.28±0.57) N·mm at 50 ℃ under 25 MPa for 20 min. The higher the temperature of DPCD treatment, the lower the least gelation concentration of myosin was, and the higher the shrimp surimi gel strength was. The pressure of DPCD treatment had a little effect on the least gelation concentration of myosin, but the higher pressure could increase the gel strength of myosin and shrimp surimi. When DPCD induced the shrimp surimi to form gel at the lower pressure of 5-10 MPa, the heating effect was main and the molecular effect of carbon dioxide was weak. However, when DPCD induced the shrimp surimi to form gel at the higher pressure of above 10 MPa, the heating effect and the molecular effect of carbon dioxide were cooperative. The results will provide the basic data for clarifying the mechanism of forming gel induced by DPCD.