Abstract: The relative neutron flux density distribution is one of the essential physical parameters of the reactor. Measuring the relative neutron flux density distribution of the annular fuel zero-power reactor core has guiding significance for understanding the physical characteristics of the annular fuel core reactor and conducting safety analysis. In this paper, the γ activity of the gold foil at different positions on the outer surface of the fuel cell after irradiation was measured by foil activation method under polygonal loading of annular fuel core. The axial and radial relative neutron flux density distributions of fuel cell at different positions were obtained, and the measured values were compared with the values calculated by Monte Carlo theory. The results show that the maximum relative deviation between experimental measurement and theoretical calculation is within 12%. The measurement results of relative neutron flux density distribution are in line with the measure design expectations. The existing Monte Carlo analysis methods can better analyze the axial flux density distribution of the components in the reactor. This study provides essential data support for the engineering application of annular fuel.