Abstract: In order to completely know the microst ructure and physical characteristics of silicon dioxide/ wood composites , X-ray diff raction (XRD) and energy dispersive X-ray analyzer ( EDAX) are used for studying the microst ructure of silicon dioxide/ wood composites made by sol-gel. St ress relaxation , dielect ric properties , thermogravimet ry and surface microhardness mensurating methods are used for analyzing their physical properties. Theresult s show that silicon dioxide exist s in the cell wall of wood for silicon dioxide/ wood composites made by thewood of moisture content under the fibre saturation point . Crystallinity decreases , while the mole f raction of silicondioxide increases with the enhancement of mass gain. The position of XRD spect ra peak is the same as the unt reatment . The magnitude of st ress relaxation of silicon dioxide/ wood composites is less than the unt reatment . There isa cross-linking between wood molecule and silicon dioxide. The dielect ric constant decreases , while the dielect ricloss factor increases firstly , then decreases with increasing f requency. The f requency of the dielect ric loss factorreaching the maximum value is in the vicinity of log f = 6. 5 Hz at room temperature. The start temperature of fastthermogravimet ry of the silicon dioxide/ wood composites rises in the thermogravimet ry course , their remainder massincreases in the end , and their surface microhardness increases.