An innovation UV irradiation device was used to detect the germicidal efficacy of UV irradiation on microorganisms inside the condensed milk barrel. In terms of germicidal rates, experiments were conducted to investigate the disinfecting feasibility and the effectiveness of ultraviolet under 60 experimental conditions, which were formed by 4×5×3 factorial combinations of radiant intensity, radiant time and radiant distance. The results indicated the germicidal rate was positively correlated with the radiant intensity, radiant time and radiant distance. Meanwhile, it was up to 99.9% for 90 second by UV irradiation in the same light with the radiant intensity above 90 μW/cm², when the initial consistence of bacteria in the barrel is about 10⁴ CFU/cm². It also showed the bacteria reaction order was among 1.00 and 1.04. The ultraviolet disinfection process can be viewed as first order kinetics of optical biochemistry. The first sterilization rate constant of bacteria equals to 0.34~0.37 cm²/(mW·s). The killing logarithm value was higher than 3.00. These results showed the device is effective in sterilizing.