Abstract: Five thawing treatments of sea bass(ultrasonic microwave thawing,ultrasonic far-infrared thawing,ultrasonic ohmic thawing,ultrasonic vacuum thawing,and ultrasound thawing)were compared with fresh fish,and the effects of different thawing methods on the quality of sea bass were studied. The changes of water holding capacity,freshness,lipid oxidation degree,protein thermal stability,gel properties,water distribution and microstructure of thawed fish were analyzed mainly in this article. The results showed that the thawing loss rate and cooking loss rate were significantly different in different treatments(P<0.05). The thawing loss rate and cooking loss rate of fish by ultrasonic microwave thawing were the lowest,1.52% and 13.13% respectively. The results of LF-NMR showed that in the samples thawed by ultrasonic microwave,the water migration from intracellular water to free water was less,indicating that the water holding capacity of the fish thawed by ultrasonic microwave was stronger. The pH values of all thawed samples were not significantly different from fresh samples(P>0.05)and the TVB-N values were all below 15 mg/100 g,maintaining a high degree of freshness. However,The TBARS values of the fish thawed by ultrasonic far-infrared,ultrasonic ohmic,ultrasonic vacuum and ultrasound were significantly increased(P<0.05),indicating a higher degree of lipid oxidation. The sea bass of ultrasonic microwave thawing and ultrasonic far-infrared thawing had higher thermal stability,viscoelasticity,and the microstructures were more dense and smooth. But the myofibril bundles were slightly crimped by ultrasonic vacuum thawing,and the fibers by ultrasonic ohmic thawing and ultrasonic thawing had rough surface and loose structure.