Abstract: Fat greenling,Hexagrammos otakii(average length of 5,8 and 11 cm) were tagged with three kinds of T-bar tags(T1,T2,T3).The survival rate,tag-shedding rate,swimming and feeding behavior,growth performance of fat greenling juveniles post tagging were observed and recorded.Based on these data,we determined the suitable T-bar tag for fat greenling juveniles at different size.the results showed that fat greenling juveniles with total length less than 5 cm were not suitable for tagged releasing;the T1 tags were suitable for fat greenling juveniles with average length of 8 cm with tag-shedding rate of 4.83%,survival rate of 97.17%;the T1 and T2 tags were suitable for fat greenling juveniles with average length of 11 cm with tag-shedding rate of 2.00% and 5.67%,survival rate of 100% and 95.83%.In June 2017,the experiment of tagged releasing was carried out in Yantai offshore,using the fat greenling juveniles with T1 tags,and achieved good tagging results.