Abstract: The MCNPX2.5.0 used for high energy particle transport was adopted to calculate the dose rate of the samples. The samples were vertically located in the 3 meters away from the center point of the dual plate source rack in the irradiation room. The geometric model of Co-60 irradiation device was built in the Monte Carlo simulation. According to the actual situation, two kinds of working conditions with or without irradiation products in the irradiation room were set. The absorbed dose rates of the three kinds of samples were calculated. Firstly, the absorbed dose of 12 kinds of samples with different packaging specifications and different weight were calculated in the different irradiation time. Secondly, the absorbed dose rate of 10 kinds of samples with the same specification and with different weight were calculated. Thirdly, the absorbed dose rate of 9 kinds of samples with different specifications but with the same quality were calculated. The results show that the value of the working condition without irradiation products is 4.19 times larger than working condition with irradiation products. The absorbed dose rate and its variation law of three kinds of samples can be used as reference for actual production. The MCNPX simulation method has important practical signification for irradiation of new products.