Grass carp fillets treated with ozone were packed with vacuum package(Ⅰ),100% CO2 package(Ⅱ),75% CO2+25% N2package(Ⅲ),55% CO2+45% N2 package(Ⅳ),respectively and then stored at control freezing-point temperature.Changes of total bacteria,microbial composition,TVB-N value,TBA value,sensory quality,drop loss rate,and texture properties of grass carp fillets during controlled freezing-point storage were studied.The results showed that vacuum package and 100% CO2 package had remarkable inhibition on the bacteria growth and quality of grass carp fillets.The TVB-N value of grass carp fillets with vacuum package and 100% CO2 package under the control freezing-point temperature storage after 28 days were maintained the first grade quality.However,the drop loss rate of grass carp fillets with 100% CO2 package was lower than that with vacuum package.During controlled freezing-point storage,Gram-positive bacterium in grass carp fillets increased while gram-negative bacterium decreased.The effect of CO2 inhibition on the growth of total bacteria increases with the increase of its concentration.