The sol-gel process of 1,8-bis(triethoxysilyl)octane (TES-Oct) catalyzed by phosphotungstic acid (PWA) has been investigated by time-resolved dynamic light scattering. The time-intensity correlation functions (ICF) exhibited two modes, corresponding to the cooperative diffusion of entangled chains and the translational diffusion of cross-linked clusters. Below the gelation threshold the ICFs were well described by sum of two exponential functions, allowing the successful analysis of the relaxation times and the corresponding relative intensity for the fast and slow modes. On the contrary to general observation of acid-catalyzed systems, the specific gelation process was found for r(PWA) = 0.100, the molar ratio of PWA to TES-Oct. Namely, the relative amplitude for the fast relaxation, A(f), and the averaged slow relaxation time, , exhibit exceptionally larger values in the gelation process, suggesting the existence of the ionized larger clusters as found for the base-catalyzed system. The hydrodynamic radii, R-H, were also evaluated by dilution of the gel forming samples at several sampling points in order to confirm the existence of the larger cluster during gelation. In addition to the normal increase in R-H in the sol-gel process, it was found that the matrix viscosity and/or hydrodynamic interaction play a significant role in both the slow dynamics, e.g., divergence of in the gelation process and a power law behavior in the ICF around gelation threshold, in this system.