Low power X-ray irradiator was used to irradiate the microorganisms in contaminated fresh beef from 3.08 to 18.48 Gy. D₁₀ values were gained by correlation analysis of microbial survival rate and irradiation dose in this condition. The radiation sensitivity of them was also discussed. The results showed that: theD₁₀ values for environmental polluted bacteria strains of Escherichia coil, Bacillus cereus and its spores were5.41, 5.00 and 23.81 Gy respectively. TheD₁₀ values for pathogenic bacteria strains of Staphylococcus aureus and Listeria monocytogenes were 5.35 and 6.45 Gy respectively. The D₁₀ values for spoilage bacteria strains of Pseudomonas fluorescens, Pseudomonas aeruginosa and spores of Penicillium were 3.62，4.39，and 16.39 Gy respectively. Among the strains tested, spores of Bacillus cereus and Penicillium were more resistant to irradiation. Pseudomonas fluorescens and Pseudomonas aeruginosa were more sensitive to irradiation. After being irradiated by low power Xray, the strains tested still had some bactericidal effects.