Abstract: In the high pressure and low temperature conditions during the production and transportation of deep-sea oil and gas, hydrate is formed easily, which could cause pipeline blockage. Herein, for gas-liquid-solid flow system of hydrate slurry, the hydrate particles are classified according to the particle size based on the characteristics of the dispersed phase. In combination with the kinetics model of hydrate formation/decomposition, the number, size and movement laws of the hydrate particles were simulated, the two-fluid model and the temperature equation were coupled, and a multiphase transient flow mechanism model of hydrate slurry applicable to the oil-dominated flowlines was established. The governing equations were discretized by a staggered grid, and the coupled solution of multi-physics fields covering the multi-phase flow, the dynamic change of hydrate particle formation/decomposition and the movement of hydrate particles was realized on the basis of the pressure-based algorithm. By applying the model to a multiphase transportation pipeline, the change of the hydrate volume fraction were obtained, which could provide theoretical basis to the quantitative analysis on the blockage risk of hydrate slurry transportation.