Abstract: Using the uniform experiment,fresh-keeping effect of CO2,O2 and N2 at different ratios on fresh meat products at（3±1） °C was investigated.Bacterial count was determined after 18 d,and the reciprocal of logarithm of bacterial count was analyzed.The result showed the optimal ratio of CO2,O2 and N2 was 75：10：15.This modified atmosphere package made fresh port maintain second-grade freshness within 18 d.