UPR composites were prepared with nanomaterials as toughening agent. The effect of nanoparticles to toughen UPR composites was studied. The tensile test results showed that at a certain range the toughening effect becomes better with the increasement of organic rigid particle PA6 and inorganic rigid nanoparticles SiO2. The single cell constitutive model of the rigid particles and UPR phase was established. The macro-plastic deformation was simulated by the relevance of micro-mechanical and macroscopic mechanical parameters, the simulation curves were in good agreement with the experimental ones. The numerical results indicated that the nonlinear theoretical model can efficiently simulate the plastic strain curves of the composites.