Highly dispersed CuO nanoparticles were successfully synthesized within mesoporous silica in supercritical CO2 using inorganic Cu precursors. Co-solvent and deposition time were found to have significant influence on the metal loading and the morphology of the nanophase. The agglomerates of nanoparticle outside the SBA-15 channels were obtained, whose size were about 20-80 nm, when ethanol, 1,3 propylene glycol and n-butyl alcohol were used as co-solvent, although the inorganic precursor has large solubility in them. When ethylene glycol was used as co-solvents, large amounts of continuous nanowires were found inside the SBA-15 channels. However, when the mixture of ethylene glycol and water were used as co-solvent, short nanorods or even nanoparticles were found instead. It indicates that the role of the co-solvent may have many aspects, such as enhancement of the precursor dissolution, change of the interaction between the precursor and the substrates and so on. In addition, it was found that a larger amount of co-solvent had negative effect on the metal loading, mainly due to the phase separation of the ternary system of supercritical CO2, co-solvent and inorganic precursors.