This paper presents the synthesis, characterization and molecular simulation of the silica hollow spheres (SHSs). The SHSs have been prepared using a double-template method, in which the calcium carbonate nanoparticles (CaCO3) serve as core templates and the cetyltrimethyl-ammonium bromide (CTAB) as wall structure-directing agents. The TEM, XRD, and nitrogen adsorption have been employed to characterize morphologies and structures of the SHSs. The experimental results indicate that the as-prepared sample has an average external diameter of about 85 nm and has occurrence of disordered mesopores in the walls. In the simulation, the SHSs have been modeled as cylindrical pore with pore size distribution according to the experimental data. A combined method of grand canonical Monte Carlo (GCMC) simulation and statistics integral equation (SIE) has been carried out to determine the pore size distribution (PSD) of the SHSs based on the experimental adsorption data of nitrogen at 77 K. The results show that the PSD simulated data are in a good agreement with the experiment, which means that the proposed model for the SHSs is reliable and the combined method of GCMC and SIE is powerful for evaluation of the PSD of the silica hollow spheres. (C) 2004 Elsevier B.V. All rights reserved.