The sliver nanoparticles (n-Ag) were synthesized in-situ in bisphenol-A epoxy resin(E-51) by acetaldehyde at 80 ℃. The size, size distribution and conglomeration behavior of n-Ag were observed by freeze-etching replication transmission electron microscopy(FRTEM). The centrifuge tests were used for evaluating the dispersion and dispersion stability of n-Ag. The microwave-absorbing properties of n-Ag synthesized in-situ and the microwave curing performance of epoxy resin dispersion system containing n-Ag were studied by pulse microwave. The toughening modification effect of epoxy resin were evaluated by tensile test. The results show that n-Ag is composed of spherical particles with a homogeneity and the average size of 30 nm. The n-Ag can maintain stability, no sedimentation and no agglomeration appear in the dispersion system. n-Ag synthesized in-situ have a good microwave-absorbing property, and it can obviously decrease the microwave curing time of modified epoxy resin. The curing time of 2.5% n-Ag epoxy resin is 38% less compared to that of epoxy resin. The microwave curing rate of n-Ag epoxy resin dispersion system is several times faster than the traditional heating curing. The silver nanoparticles have a significant toughening function to epoxy resin. The toughening effect to epoxy resin is best when the mass ratio of the resin to ultra-dispersion-stability n-Ag is 2% to 2.5%. Under this situation, fracture elongation of the composite material increases by about 110%-130% compared with unmodified resin