Abstract: The gas mixture ratio of modified atmosphere packaging for chilled meat was optimized to strengthen preservation effects.Based on simplex- centriod design,total bacteria count,total volatile basic nitrogen( TVB- N)value,p H value and sensory score were used as indices to evaluate the effect of gas mixture ratio( O₂,CO₂ and N₂) on chilled meat.Compared with the control group of pallet packing,a fitting mixture of gas could obviously inhibit bacterial growth,reduce TVB- N production and maintain sensory quality. The indices showed significant correlations with each other( p < 0.01).Total bacteria count,TVB- N value and their weighted value measured at the 8^th day and the 10^th day were selected to establish six regression mathematical models with three factors including O₂ percentage,CO₂ percentage and N₂ percentage,followed by optimizing the gas mixture ratio independently.The optimum gas ratio was confirmed to be 22% O₂ and 78% CO₂ after comparative investigation on the preservation effects on chilled meat.Under this condition,the total bacteria count and TVB- N value of chilled meat kept at the 8th day was respectively 5.85 lg( cfu / g) and 14.00 mg /100 g,and the shelf life comparing with that of pallet packing was extended for 5 days.