Abstract: To evaluate the effects of phosphate-free improved water retention agent(composed by 1.5% NaCl,0.5% trehalose and 2% sodium citrate)on the frozen quality of Mytilus edulis Linnaeus,using distilled water group as a blank control,compound phosphate group as a condition control. Results showed that:After 25 d of storage(-18℃),the results indicated that treated by phosphate-free improved water retention agent,the water loss,thawing loss and cooking loss of mussels were obviously decreased and the rate of soaking and weight gain was increased,there was no obvious difference in water loss reduction when compared with compound phosphate group(p>0.05),and compound phosphate had advantage in improving the soaking weight gain. The L^* value of mussels kept decreasing and TVB-N value of mussel rised in frozen storage,L^* values of mussels that treated with phosphate-free improved water retention agent maintain well,and significantly better than other groups(p<0.05),meanwhile,TVB-N value of mussels rised slowly,and obviously lower than other groups.While,phosphate-free improved water retention agent could reduce the loss of Ca²⁺-ATPase activity and the loss of myofibrillarr protein effectively,and obviously better than distilled water group and compound phosphate group. In snmmary,that phosphate-free improved water retention agent can effectively improve the quality of mussel.