Abstract: Addressing the issue of porosity evolution during the curing process of thermoset composites, a simulation model has been developed to describe the flow-compaction behavior of the composites, aiming to predict changes in porosity throughout the curing process. Initially, a multi-field coupling model encompassing sub-models for thermo-chemical, fiber bed compression, pore compression, and percolation flow was established. This model accurately describes the changes in porosity within the composites during the flow-compaction process. The UMAT subroutine of the ABAQUS finite element analysis software was utilized to integrate these sub-models into the software. The validity of the simulation model was verified through corresponding experimental porosity measurements. The research further indicates that the porosity at the fillet of L-shaped composite components is higher than that in flat areas due to insufficient shear slip capacity. In the simulation model, the stiffness of the fiber bed, viscosity, inter-ply friction coefficient and curing pressure play important roles in the change of porosity.