After silicate impregnation, the content and distribution of elements in the modifier is an important index to evaluate the impregnation effect, which plays an important role in the physical and mechanical properties of the modified Chinese fir. The effects of the biomimetic respiration method on the density, bending strength, compressive strength, three section hardness and 24 h water absorption of silicate modified Chinese fir were studied. The chemical composition and structure of unmodified and modified Chinese fir were analyzed by XPS and FTIR, and the distribution depth and law of silicate modifier in the modified Chinese fir were discussed. The results showed that the average density of the modified Chinese fir was more than 0.721 g·cm-3, the bending strength and compressive strength increased by 170.19% and 286.64%, respectively. The hardness of the transverse section, radial section and tangential section of the modified Chinese fir increased in different degrees. The 24h water absorption of Chinese fir decreased from 91.17%±2.51% to 39.23%±1.62% after silicate modification, which indicated that the dimensional stability of Chinese fir was greatly improved. Compared with the unmodified Chinese fir, the absorption peaks of Na and Si elements appear in the XPS full-spectrum scanning of the modified Chinese fir wood, and the chemical structures of Si—O—C and Na-O appear in the narrow spectrum scanning. At the same time, the absorption peak of Si—O—Si appeared in the FTIR spectrum of the modified Chinese fir wood, the content of free hydroxyl decreased, and the associated hydroxyl increased. XPS and FTIR analysis showed that silicates were impregnated into the pores of Chinese fir wood, and sodium silicate formed a chemical bond and hydrogen bond with hydroxyl in Chinese fir wood. This was also an important reason for the improvement of mechanical properties and water resistance of modified Chinese fir. In addition, it was found by XPS that C, O, Na and Si elements appeared along the transverse direction from the surface to 30 mm. The absorption peak intensity of Si—O—C bonding structure was basically the same from the surface to 30 mm, which indicated that the chemical bond between sodium silicate and hydroxyl groups in Chinese fir wood was formed more evenly from the surface to the middle part.It was found that the relative contents of C, O, Na and Si element in the modified Chinese fir wood were slightly different from the surface to the middle part (30 mm). The results showed that the modifier was in the middle of Chinese fir wood, and the uniformity was good. The research results will provide data support for the impregnation modification effect of Chinese fir, and provide the basis for optimizing the modification process and method, and further improving the physical and mechanical properties of modified Chinese fir.