The synergistic toughening of UPR composite by rigid particles of organic PA6 and inorganic nano-SiO2 was studied. The effects of PA6 and SiO2 on the notched impact and tensile strength of the UPR composite were studied by means of the mechanical properties test. The experimental results indicated that the notched impact strength was improved and its effect was evident when 7-9％rigid particles were applied and the tensile strength was improved when the 2-5％ rigid particles were applied. The composite of PA6/SiO2 ( 2/1) exhibited good mechanical property in the synergistic toughening. By the micromechanical analysis of composite, we thought that the stiffness of composite materials was determined by the stress suffered the rigid particles and the deformation of UPR polymer phase.