Lost circulation usually happens when drill through fractured formation. A clear understanding of the circulation loss mechanism is key to successful drilling operations. More attention has been paid to fracture development and lost circulation materials (LCMs) composition. Much work still needs to be done on how the solid particles affect the overall fluid loss process in rough-walled fractures. The control equations for liquid-solid multiphase flow in a 2D rough-walled stationary fracture were established based on fundamental principles of fluid mechanics. Among these equations, the drilling fluid was treated as a Bingham type non-Newtonian fluid, and the influence of solid particles on fluid flow was analyzed in detail. The finite difference method was adopted to the numerical solution of the equations, and the impact of such working parameters as fracture dimensions, bottomhole pressure differential, physical properties of both fluid and particle on the fluid loss were analyzed. The following conclusions can be drawn from the paper: (1) the presence of solid particles can lower the leakoff rate and accumulative leakoff rate to various degrees; (2) the larger the fracture dimension, the lower the leakoff rate and accumulative leakoff rate; (3) the larger the pressure differential, the higher the leakoff rate and accumulative leakoff rate; (4) the leakoff rate and accumulative leakoff rate will decrease with the increase of particle diameter and its volume concentration; (5) particle sphericity and yield stress have little influence on the leakoff rate and accumulative leakoff rate. (6) The higher the plastic viscosity of drilling fluid, the lower the leakoff rate and accumulative leakoff rate. The limitations of this study, suggested improvement and future direction of current work are also highlighted. (c) 2019 Elsevier B.V. All rights reserved.