Abstract: In this paper, a double-logarithmic polynomial was used to fit four measured efficiency data of germanium detector, the fitting detection efficiency and its relative standard uncertainty were calculated, and the main factors affecting the fitting detection efficiency uncertainty were analyzed. The result shows that five- or six-order logarithmic polynomial can well fit the measured data in 6-2754 keV. Within the measured energy range, the uncertainty of the fitting value is mainly influenced by the uncertainty and density of measured data. The uncertainty of fitting value is low in the area where measured data are accurate and dense, and is high in the area where measured data are inaccurate and sparse. Outside the energy range of experimental data, the uncertainty of the fitting value increases rapidly, therefore it is not appropriate to use double-logarithmic polynomial to get γ detection efficiency.