Abstract Under the action of laser pulses with a wavelength of 647 nm and a pulse duration of 150 fs, the optical transient response of an Ag−O−Ba thin film was obtained by the pump-probe method. Optical relaxation is a process in which non-equilibrium electrons, excited by laser pulses and originating from metallic ultrafine particles, return to the equilibrium state. The optical transient relaxation of an Ag−O−Ba thin film consists of fast and slow parts. The fast part occurs in 200 fs and is caused by non-equilibrium electrons entering the matrix. The slow part occurs in 1.6 ps and is caused by non-equilibrium electrons scattering within the lattice and interface between the Ag ultrafine particles and the matrix.