The effects of high pressure processing(HPP)(0,50,150,300,450 and 600 MPa for 15 min)on the sensory quality,color,firmness,pH,amino nitrogen,Ca² -ATPase activity and ultrastructure of Aristichthys nobilis muscle were investigated.The odor,taste and chewiness were modified by HPP,and the sensory quality improved significantly after treatment at 300,450 or 600 MPa(P＜0.05). L* and b* value increased while a* reduced after HPP.The firmness of the muscle increased pronouncedly(P<0.05)with pressure beyond 150 MPa.HPP treated samples had higher content of amino nitrogen(P<0.05)compared to the control with increases of 15.19% and 17.89% for 50 and 300 MPa pressurized samples,respectively.pH showed a positive correlation with the pressure.The activity of Ca² -ATPase was inhibited by HPP,and pressures beyond 150 MPa inactivated Ca² -ATPase more rapidly.Moreover,HPP had a great impact on ultrastructure of A. nobilis muscle.After treatment at 150 MPa,sarcomeres contracted and myofibrils looked thicker than the control.In addition,disappearance of Z-line, M-line and H-zone and breakage of A-band and I-band were observed.The structure of sarcomeres was completely destroyed,intermyofibrillar space disappeared and gelation of myofibrils was observed when pressurized by 450 MPa.Our results indicated that the HPP could serve as a promising technique for commercial quality enhancement of A. nobilis muscle.