Effects of thermal treatment on the third-order optical nonlinearity and ultrafast dynamics of Ag nanoparticles embedded in glasses were investigated by femtosecond time-resolved OKE and femtosecond pump-probe techniques. The results indicate that the third-order susceptibility increases from 1.1 x 10(-11) esu to 1.48 x 10(-9) esu with increasing the annealing temperature. The fast decay process is accelerated and its amplitude ratio increases with the thermal treatment, which could be attributed to an increase of the electron-phonon coupling through the process of treelike Ag nanoparticle aggregation. The slow relaxation time ranges from 25 ps to 140 ps, depending on the thermal conductivity of the matrix material. (C) 2009 Published by Elsevier B.V.