The femtosecond laser pulses and pump-probe method have been used to measure the transient change of transmissivity of metallic ultrafine particles(UFPs) embedded in semiconductor thin film (Ag-BaO). The phenomena that the optical absorption of the films decreases and then restores within 2ps have been observed. The phenomena are due to the fact that electrons near the Fermi energy level in Ag UFPs are excited by femtosecond laser pulses and then the generated nonequilibrium electrons undergo a transient relaxation. The relaxation includes includes two parts: first, nonequilibrium electrons from Ag UFPs enter the matrix;then,nonequilibrium electrons are scattered by the lattice and inter-face between the Ag UFPs and the matrix. The different diameters of Ag UFPs affter the relaxation time of nonequilibrium electrons.