Abstract: The sediment in crude oil pipeline will easily lead to a blockage, therefore the detection of sediment thickness in oil pipeline become an important technology issue. The experimental measurement device is composed of ¹³⁷Csγ radioactive source and NaI (Tl) scintillation crystal detector. In this paper, researchers study the transmission characteristics of paraffin in different thicknesses through simulating the sediment with a cylindrical paraffin and transmitting the paraffin with γ-ray, and establish an empirical formula between transmission intensity and paraffin thickness, with a linear correlation coefficient 0.996 3. The results show that γ-ray transmission method is sensitive to the sediment thickness, and can be used in oil pipeline for non-destructive test purpose.