Metallic nanoparticle (NP) shapes have a significant influence on the property of composite embedded with metallic NPs.Swift heavy ion irradiation is an effective way to modify shapes of metallic NPs embedded in an amorphous matrix.We investigate the shape deformation of Ag NPs with irradiation fluence,and 357MeV Ni ions are used to irradiate the silica containing Ag NPs,which are prepared by ion implantation and vacuum annealing.The UV-vis results show that the surface plasmon resonance (SPR) peak from Ag NPs shifts from 400 to 377nm.The SPR peak has a significant shift at fluence lower than 1 × 1014 ions/cm2 and shows less shift at fluence higher than 1 × 1014 ions/cm2.The TEM results reveal that the shapes of Ag NPs also show significant deformation at fluence lower than 1 × 1014 ions/cm2 and show less deformation at fluence higher than 1 × 1014 ions/cm2.The blue shift of the SPR peak is considered to be the consequence of defect production and Ag NP shape deformation.Based on the thermal spike model calculation,the temperature of the silica surrounding Ag particles first increases rapidly,then the region of Ag NPs close to the interface of Ag/silica is gradually heated.Therefore,the driven force of Ag NPs deformation is considered as the volume expansion of the first heated silica layer surrounding Ag NPs.