Abstract: This paper presents and analyzes the methods of hydraulic calculation of pipes in oil loading and unloading of road tanker, in order to provide reasonable guidance for petroleum and petrochemical companies in pipe diameter design and pump selection. Through theoretical analysis, the theoretical foundation and calculation ideas/steps of three methods (i.e. simplified calculation method, accurate calculation method, and software simulation method) are expounded, and the error sources of the calculation results are elaborated. With typical calculation examples, applicable conditions and precautions of above three methods are comparatively summarized. After the analysis, it is found that these methods basically follow the same theoretical foundations, but derive different results, which is mainly attributed to different oil flowrate at each pipe section in calculation process. For the average oil loading and unloading conditions, all three methods above are applicable; when the higher requirements exist for calculation accuracy of pipeline length, complexity and pump NPSH, the simulation method is recommended for hydraulic calculation.