Abstract: In order to study the relationship between water distribution and quaiity of tilapia fillets affected by different ultrasonic wave( 200,250,300,350,400,450 and 500 W),the thawing time,thawing loss,p H,TBA value,Ca2 +- ATPase activity,transversal relaxation time T2 were measured,and the correlations between water distribution and quality were also analyzed.The results showed that with the increasing of the ultrasonic wave( except the 300 W),the A21 of immobilized water increased pronouncedly( p < 0.05).The p H,TBA value,Ca2 +- ATPase activity had a significant negative correlation with thawing time and thawing loss( p < 0.01).Also there was a negative correlation between TBA value with T22( p <0.05). Compared with the control( the running water thawing),the 450 W of ultrasonic wave was more suitable to maintain the quality of tilapia fillets through thawing time,thawing loss,Ca2 +- ATPase activity improving respectively by 62.67%,56.04%,23.42%.The transverse relaxation time T21 of immobilized water was shortest,indicated that the mobility of water was lowered and the water hoiding capacity was improved.So it is feasible to thaw the tilapia fillets by the appropriate conditions of ultrasonic and there is a better effect by the 450 W of ultrasonic wave.What's more,the results will provide reference on application in the same kind of frozen aquatic products thawed by ultrasonic wave.