Migration of Au nanoparticles by thermal diffusion into porous SiO2 matrix substrates has been studied using secondary ion mass spectroscopy (SIMS). When the samples having four different porosities were annealed at T = 410 K for 1.5 h, no noticeable variations in the thermal diffusion of Au nanoparticles were observed. All the measured diffusion coefficients of Au particles, were an order of 10(-15) cm2/s at 300-410 K in a very limited interfacial region. Regardless of their porosities, the pores must be discontinuous, which acts as a diffusion barrier to block the continuous diffusion of Au particles.