<p>Fractures are important seepage channels in oil and gas extraction and are the key to efficient resource exploitation. However, with the extensive development of fractures, they have also become the main cause of severe drilling fluid and oil and gas leakage. In order to enhance the leakage control of fractured strata, the plugging mechanism was studied through the computational fluid dynamics - discrete element method (CFD-DEM) numerical simulation. This paper focused on the spherical particle diameter, concentration dose, gradation, fluid density and velocity. The research found that for monodisperse particles, under the condition of R = 0.4, the best blocking efficiency can be achieved through sequential double-particle bridging. A concentration of 15% was determined to be the most effective dose. When mixed particle sizes form multi-level sealing layers, they can adapt to different fracturing conditions. In addition, the particle transport mechanics in the crack was controlled by the fluid density. When the density range of particles was between 1.80 and 2.20 g/cm³, the probability of retention in the crack was high and the formed leak-stopping layer was the longest. In this study, the best leak-stopping effect was achieved at a speed of 0.8 m/s by minimizing the migration velocity and maximizing the sealing integrity. Ultimately, the results indicated that particle size, concentration and gradation were the key factors affecting the effectiveness of plugging.</p>