The stability of plugging zone has a great impact on the lost circulation control effect in fractured reservoirs. In this work, the multiscale structure of plugging zone is described based on the analysis of its inter-particle forces. Structure characterization methods of plugging zone are developed accounting for geological characteristics and drilling operation features of fractured reservoirs. To conclude, fracture plugging zone is a dense granular matter system, and the contact forces are dominant in inter-particle forces. Plugging zone structure is multiscale, of which the microscale is single lost circulation materials (LCM), mesoscale refers to the particle cluster transferring force chains, and the macroscale refers to the plugging zone formed in the fracture. The correlation between performance parameters of microscale LCM and strength of macroscale plugging zone can be established by characterizing the mesoscale structures of plugging zone. This study provides the basis for LCM research and development in fractured reservoirs. (C) 2020 Elsevier B.V. All rights reserved.