Sintering-free and carbon-free Ni catalysts developments are hot topics for high temperature hydrocarbons catalytic reactions. Core-shell is a promising structure to limit sintering, but ineffective towards carbon deposition if big sized Ni nanoparticles are present. In this work, core-shell structured Ni@SiO2 catalysts with small-sized Ni nanoparticles (about 5 nm) were synthesized by microemulsion method, which are featured by both sintering-free and low carbon deposits for high temperature CO2 reforming with methane reaction. The advantages were originated from the silica shell overlay confined moving space of Ni nanoparticles and the small size of Ni nanoparticles guaranteed low carbon diffusion in Ni crystals. The work provides a simple approach to synthesize small-sized Ni nanoparticles in core-shell catalysts for stable performance of CO2 reforming with methane reaction. It is supposed that this type of catalyst could also be applied in many other hydrocarbon catalytic reactions involving sintering and carbon problems.