A novel, hyperbranched polysiloxane (HBPSi) is successfully synthesized via hydrolysis using γ-methacryloxypropyl trimethoxysilane (A174) and deionized water, under catalyst-free conditions. Then, for the first time, the HBPSis are used to modify a 3D printing light-curing epoxy resin. Thermogravimetry results showed that the addition of HBPSi improved the heat resistance of the epoxy resin. Experimental results also show that the addition of HBPSi simultaneously improves tensile strength, elongation at break, and impact strength. In particular, a great increase in the toughness of 3D printing light-curing epoxy resin is observed, with 5 wt % HBPSi loading. These results indicate that the HBPSi containg OH- and Si-O-Si can be potentially effective at improving the performance of the 3D printing light-curing epoxy resin. This investigation suggests that the method proposed herein is a new approach to develop the performance of 3D printing light-curing epoxy resin for cutting-edge industries, especially those that simultaneously have outstanding thermal resistance and toughness.