Abstract: The research on the sand carrying mechanism of multiphase mixed transport is the key to prevent the formation of blockage of gas-liquid-solid slurry in the flow system of multiphase mixed transport in the process of offshore oil & gas development and natural gas hydrate exploitation. At present, the phenomenon of sand production often occurs in the process of oil & gas development and hydrate exploitation. In this paper, the experimental results on the critical sand carrying of gas-liquid-sand multiphase in multi-angle pipelines were systematically summarized. Based on this, the critical sand carrying mechanism of gas-liquid-sand multiphase in multi-angle pipelines and the key influence parameters of critical sand carrying flow rate (including pipeline inclination angle, pipe diameter, liquid viscosity and particle volume fraction) were reviewed. In addition, the research progress on the calculation of the drag coefficient of critical sand carrying flow rate was deeply analyzed and summarized, so as to provide the theory basis for avoiding the safety problems caused by sand production in the process of oil & gas development and hydrate exploitation. Finally, the problems existing in the current studies and the future research directions were pointed out.