Abstract: The seabed shipment crude oil pipeline in Sudan 3/7 Block is a submarine pipeline. The transportation process of the pipeline is alternately replaced by the crude oil shipment and diesel. According to the characteristics of transportation process, the experimental model and theoretical model are integrated to simulate the change laws of wax thickness and temperature along the pipeline in shipment period and the relationship between the dissolved amount of wax and the flowrate of diesel in the substitution process of diesel in non-shipment period. Results show that the longer the time of shiploading is, the thicker the layer of wax deposition is, and the amount of wax deposition per unit time is declined. The greater the displaced flowrate of diesel is, the better the dissolved effectiveness of wax layer is. Considering the energy consumption in the replacing process of diesel and the scouring effectiveness to the wax deposition layer synthetically, the economical replacing flowrate of diesel is 2 m/s. Analyzing the law of wax deposition and decomposition will be an effective way to study the law of wax deposition in the similar pipeline operating conditions.