Detection efficiency of HPGe γ spectrometer is an important performance and has a greater impact on radioactivity measurement results of soil samples.By measuring γ-rays from 210Pb(46.5 keV)

214Pb(351.9 keV)

7Be(477.6 keV) and 137Cs(661.7 keV) in soil samples of 15–95 mm in thickness(solid angles of ~100°– ~60°)

the relationship were investigated between the sample thickness and the γ-ray counts obtained by efficiency calibration or comparative measurements.The results showed that the detection efficiency decreases with increasing sample thicknesses

with the largest ratio(3.5) of maximum/minimum detection efficiency at 46.6 keV and the smallest(2.2) at 661.7 keV.The detection efficiency decrease at low energies was in a logarithm way

while at high energies the detection efficiency decreased linearly.