Dental resins are currently the most commonly used filling materials for dental caries clinically due to their advantages of aesthetics, safety, and easy operation. However, their service life is limited because of their low mechanical strength and insufficient antibacterial activity. In this study, radial mesoporous silica was prepared firstly, and then loaded nanosilver into its porous channels to obtain silver loaded radial mesoporous silica (Ag-RMS). Effects of different contents of Ag-RMS on antibacterial, mechanical, and physicochemical properties of dental composite resins were studied. The results showed that Ag-RMS could significantly improve the antibacterial performance of composite resins, achieving an antibacterial rate of 99.68% against Streptococcus mutans when the addition amount of Ag-RMS was 5% (mass fraction). Mechanical strength of the composite resin gradually increased with the increase of Ag-RMS content. When the addition amount of Ag-RMS reached 7% (in mass), the flexural strength of composite resins was 28.16% higher than that of resin matrix. Moreover, the addition of Ag-RMS had almost no obvious effect on their polymerization shrinkage rate, monomer conversion rate, curing depth, and surface hydrophobicity. These results indicate that the prepared Ag-RMS in this study can improve the comprehensive performance of the novel composite resins.