Surface chemical construction changes of Chinese Fir ( Cunninghamia lanceolata ) and Poplar "Sanbei No.1"( Populus nigra×P.simonii ) treated with acetyloide were studied by using ESCA analysis. The results showed that there were great differences of surface chemical characteristics between Chinese Fir and Poplar. In the surface of Chinese Fir, the ratio of carbon atom was higher than that in Poplar, but the ratio of nitrogen atom and oxygen atom was lower than that in Poplar. Furthermore, there was calcium atom in the surface of Poplar. After reaction with acetyloide, the surface chemical characteristics of wood had been changed ; the ratio of O-C=O structure (carbon of carboxyl and ester) was increased.