Abstract: In order to solve the wax deposit problem of crude oil pipelines scientifically, the effect of oil temperature, wall temperature and flow rate on wax deposition in single-phase crude oil was investigated by performing laboratory loop test which includes testing section and reference section. Then, the wax deposit laws of waxy crude oil were summarized systematically. The sediments were divided into 5 layers from the center of the pipe to the wall by special means. Based on microscopic observation, differential scanning calorimetry (DSC) and high temperature gas chromatography (HTGC), the radial distribution differences of sediments were analyzed, including wax content, wax precipitation per temperature drop and carbon number distribution of sediments in different layers. It is shown that the closer to the pipe wall, the higher wax content of sediments and the greater mass fraction of molecules with high carbon number. And on the contrary, the closer to the conduit flow, the lower wax content of sediments and the smaller mass fraction of molecules with high carbon number. With the depositing of wax, the molecules whose carbon number is larger than the critical value diffuse to the pipe wall and precipitate, and the molecules whose carbon number is lower than the critical value diffuse back to the surface of sediment layers. The critical carbon number varies with oil product properties and deposit conditions. The research results are of practical significance for further study of wax deposition mechanisms so as to build up high-precision wax deposition prediction model.