A dose rate fitting method based on relative error segmentation is proposed to solve the problem of low dose rate error in the process of counting and dose rate data fitting. Taking the relative error as the judgment basis, the dose rate value fitting is carried out from the high dose rate area to the low dose rate area in turn, so that the relative error of the high dose rate section in the fitted dose rate value is very close to the true value, and the low dose rate area is also close to the true value in a subsection mode. The results show that the dose rate fitting conversion method is closer to the true value.