Abstract: A set of scattering γ ray photon counts corresponding to different grease stain thicknesses was obtained by using an experiment setup, which consists of a ⁶⁰Co γ radioactive source, a NaI(Tl) scintillation detector and a micro-computerized multi-channel spectrometer etc. In addition, by using Monte-Carlo program with the similar geometry, scattering γ ray photon for different grease stain thicknesses were obtained for different thickness of soil layer and different water content in the soil layer. We give out that the sensitivity of measurement was decreasing when the thickness of soil layer was increased, and moreover, the effect of water content in soil layer on measuring grease stain thickness was regular from the simulation results.