The mechanical properties and elasticplastic of samples untreated and strengthened by silica sol using nanoindentation method were tested and analyzed. And the impacts of silica sol location on micromechanical properties of wood cell wall were also analyzed in this paper. The testing results indicated that：1）the silica sol can be introduced into wood cell wall through impregnating process, and the modulus and hardness of cell wall of composite wood were 18.64 and 0.64 GPa, increased by 59% and 31% than untreated wood, respectively. 2) Two kinds of composite wood, the modified cell wall and the bulked cell wall, can be prepared through different vacuumpressure processes, and the modulus and hardness of the two kinds of composite wood had no significant differences. It was indicated clearly that the filled lumina had no effects on the nanomechanical properties of wood cell wall. 3) The cell wall morphology of the composite wood and testing curve analysis of nanoindentation showed that the wood cell wall after silica sol treated had the same relative elastic recovery rate with that of untreated wood, and still maintained the good elastic properties.