<p>This paper proposes a state-of-the-art three-dimensional Voronoi cell finite element method (3D VCFEM) aimed at investigating the mechanical properties of particle-reinforced composites (PRCs) in space under different microstructural properties. Firstly, the modified residual energy generalized function of 3D VCFEM was proposed by applying the hybrid stress element method, and the element format of the 3D Voronoi element was constructed. On this basis, the interaction between the matrix and the inclusions was considered, and the higher-order stress function including the interaction stress term was constructed. Secondly, to solve the difficulty of integrating easily due to the complexity and irregularity of the integration region in space, Delaunay tetrahedra were introduced within the 3D Voronoi element for mesh refinement. It simplified the integration process. Finally, to verify the accuracy and efficiency of the 3D VCFEM model, comparative models of 3D VCFENM and FEM were established for analysis and discussion. The stress field and strain field were compared and analyzed for the first time. An example was also given for the presence of a large number of randomly distributed inclusion particles. The results showed that under the same accuracy, 3D VCFEM had the advantages of convenient mesh delineation and high computational efficiency compared with FEM, which provided a new way of thinking to analyze the actual PCRs.</p>