Abstract: The effect of different gas concentration in modified atmosphere packaging on the beef preservation was studied.Fresh beef were stored at the different level of concentration(O2 and CO2 within 0~100% by evenly distributed).During the storage at 4 ± 1 ℃,the gas concentration in packaging,total number colonies of beef,PH value,TVB-N values,drip loss rate and color were detected and analyzed every two days.The relationship of O2,CO2 concentration,time of storage and the total colonies was created by multiple regression analysis.The results demonstrated that it was not effective using high concentration of oxygen or carbon dioxide on beef preservation,but the combination of MAP(45%O2 / 30%CO2 / 25%N2)was the best to prolong the shelf-life of the product.