Abstract: Hydraulic gradient is a key design parameter for the design of a vertical hydraulic lifting pipeline system of deep-sea mineral particles, affecting the transportation efficiency and safety of the pipeline system. The present work simulates the hydraulic transportation process of mineral particles using the computational fluid dynamics coupled with the discrete element method (CFD-DEM), which is fully verified by the comparison with the experimental data. The total hydraulic gradient is divided into three parts: the friction of the carrier fluid, the gravity of the mineral particles, and the resistance caused by particle-wall collision. Each part of the hydraulic gradient is derived and compared with the CFD-DEM results. In addition, the proportion and influencing factors of each part are discussed in detail.