The grass carps(Ctenopharyngodon idellus) with average body length of 14.8 cm and average body weight of 65.9 g were released in Dongjiang River.Before the tagging experiment,the grass carps fed with artificial feed were acclimated to aquatic grasses. Two tagging methods were employed.One was tagging with elliptic plastic tags(8 mm×5 mm×1 mm) with brass wires with the diameter of 0.14 mm,which drilled through the interstice between the first and second dorsal fin pterygiophore.The other one was clipping the left ventral fin of grass carps.The tagged grass carps were recovered from tagging trauma for about 10 days in a pool.One hundred thousand grass carps were released,and forty thousand of them were tagged,presenting 40%of the released grass carps.About one month after the release,881 grass carps were recaptured,among which 278 were the tagged ones.The percentage of tagged grass carps recaptured was 31.6%in the total recaptured grass carps,and the recapture rate was 0.695%.The food residues in the digestive tube of recaptured grass carps were aquatic plants including hyacinth roots and some kinds of algae commonly found in Linjiang section of Dongjiang River.The results indicated that released grass carps were completely acclimated in the river environment,and that the tagging and releasing techniques established in this study were effective and applicable.The keys of such techniques were as follows.(1) The tagged grass carps with a body length of 11-17 cm can be clipped at a ventral fin or tagged with elliptic plastic tags(8 mm×5 mm×1 mm) with brass wires with the diameter of 0.14 mm,drilling through the interstice between the first and second dorsal fin pterygiophore.(2) The tagged grass carps should experience a 10-day trauma treatment.(3)The grass carps fed with artificial feed pellets should be acclimated to grasses for two weeks before releasing into the river.(4) The river sections with abounding aqua-plants are suitable places for the releasing of grass carps.