The adaptive growth of compression wood (CW) leads to the changes of chemical properties of coniferous wood, which the change of microfibril angle (MFA) affects the wood mechanical properties and macromolecular deformation. In this paper, the Fourier transform infrared spectroscopy (FTIR) was explored together with mechanical loading as a means of studying the molecular responses to the loading of Masson pine CW and normal wood (NW). It is of great significance to study the molecular biological mechanism of the mechanical properties changes of the CW. The results indicated that the MFA, tensile strength along grain and modulus of elasticity of the CW were 35.17°±2.30°, (45.37±3.41) and (18.10±0.76) MPa, respectively, and were 15.15°±1.61°, (109.75±11.87) and (70.95±6.60) MPa of the NW. What is more, the strain at the break-point of the CW was three times than that of the NW. The FTIR results indicated that the wavenumber shifts of the FTIR bands at 1 161 and 3 348 cm^-1 showed an approximately linear relationship with strain. The C—O—C of cellulose at 1 161 cm^-1 band shifted to lower wavenumber with tensile strain increase, and shift rate was 2.15 and 1.52 cm^-1·dε^-1 for the CW and NW, respectively. Furthermore, the O(3)H…O(5) of cellulose intramolecular 3 348 cm^-1 bands shifted to higher wavenumber, and shift rate was 4.62 and 2.76 cm^-1·dε^-1 of the CW and NW, respectively. The shift rates of 1 161 and 3 348 cm^-1 bands of NW were more than that of CW. However, the characteristic peaks of lignin and hemicellulose were shown not to be affected. The above results indicate that the cellulose mainly provides the strength of the wood and the matrix of hemicellulose and lignin is benefited to load transform between cellulose microfibrils. Compared with the NW, the larger orientation of microfiber of the CW leads to smaller tension deformation along the direction of cellulose molecular chain, but the larger of shear deformation between microfibrils and matrix. This also leads to a large yield deformation in the tensile process of the CW, and the strain of the failure point is greater than the NW.