A multiscale modeling of a polymer composite, which is a combination of atomistic simulation and finite element structural analysis, was demonstrated. Heat curing and cross-linking reaction steps for thermosetting resins were calculated with activation energy and heat generation via molecular dynamics simulation of Materials Studio. The microscale stress–strain curves suggesting fracture mechanisms of the molecular level were also estimated and were assigned to the finite element analysis of Abaqus. Using the fracture analysis capability, the crack propagation behavior, transiting from matrix-failure to interface-failure, was investigated. The study showed the potential of the multiscale analysis to improve the quantitative aspect in design and material selection of the polymer composite, especially with respect to failure characteristics of the material, which cannot be easily grasped by material testing alone.