Abstract: In order to survey environmental soil radioactivity with γ-spectrometer, customarily, the soil samples always are fully filled in a definite-size plastic box, paying no attention to the γ-ray energy emitting from the nuclides in a sample to be analyzed. The paper presents a new filling-sample method by which the sample quantity filled in a box depends on the energies of γ-rays to be measured. The detection efficiencies of HPGe detector were calculated by using Monte-Carlo method for various γ-ray energies and at various soil sample quantities in a box, and the optimal filling-sample quantities for different-energy γ-rays from radioactive nuclides of ²³⁸U, ²³²Th, ²²⁶Ra, ⁴⁰K, are respectively obtained.