This paper introduces the methods and the results of determining the air kerma rate at different heights above the central point on the surface of radiactivity body source used by the experimental measurement methods and the Monte Carlo theoretical analog computation method.The results of this study show that the certifications of both the experimental measurements and the theoretical analog computation have a better consistency and have no distinctive systematic difference.Based on the above results,the reduction coefficient of Becquerel method is fitted in the first time,which can reflect objectively the air kerma rate per radionuclide concentration unit above China's body source standard for environmental ionizing radiation.So the accuracy of the air kerma rate above pad body source by Becquerel method is improved.