Abstract: The diffusion of n-hexane in SiO2 particles and SiO2/poly(styrene-co-acrylic acid) (SiO2/PSA) core-shell particles, prepared by phase inversion method, was investigated by constant gradient field NMR (CFG-NMR). According to the two-site modal and molecular exchange theory, 1H CFG echo decay curves of n-hexane could be fit as biexponentials, implying that two different diffusion coefficients were existed in the diffusion system. The diffusion coefficients of n-hexane in the SiO2/PSA core-shell particles were much lower than in the SiO2 particles, indicating that the poly(styrene-acrylic acid) shell played as a barrier on the diffusion of n-hexane. By varying the diffusion time in the pulsed sequence, we found that the diffusion coefficients of n-hexane in the core-shell particles were strongly depended on the diffusion time.