The femtosecond laser pulses and pump-probe method were used for measuring thetransient change of optical transmissivity of noble metal particle-matrix commpite thin films （Cu-Ba-O

An-Ba-O）. It is observed that the optical absorption in the thin films rapidly increases and then recoversin a few picaseconds. optical relaxation is a process in which nonequilibrium electrons

form metallic ultrafine particles

excited by laser pulses

return to the equilibrium state. the theoretical value of electronphonon coupling constant g of An ultra fine particles in the composite thin film is got.