Mesoporous KIT-6-supported highly dispersed silver nanoparticles and nano-networks were successfully synthesized in supercritical carbon dioxide and co-solvent solution using AgNO3 as a precursor, followed by calcinations. The nanocomposites were characterized by XRD, TEM, ICP, and N-2 adsorption-desorption isotherms. Three kinds of co-solvents were investigated including ethanol, the mixture of ethanol and ethylene glycol, and the mixture of ethanol and water. It was found that when only ethanol was used as a co-solvent, a small amount of AgNO3 was deposited onto the complex nanochannels of KIT-6 even if the deposition time was 12 h. However, it took a short deposition time of 1 h to deposit a large amount of precursors onto the substrates when the mixture of ethanol and ethylene glycol and the mixture of ethanol and water were used as co-solvents. The large solubility of AgNO3 in ethylene glycol or water had a positive effect on the dissolution of precursor in scCO(2), which was beneficial to the adsorption of precursor on the substrates.