Abstract: In this paper, the hydration process of Portland cement and CNTs reinforced samples at the early age was characterized by FTIR spectroscopy. The rustles show that FTIR is a simple and rapid research method in operation, which can reflect the basic variation in the primary cement hydration products. With the proceeding of hydration reaction, the peak value corresponding to Si-O vibrations in FTIR spectrum shifts from low wavenumbers to high wavenumbers, which not only reflects the polymerization process of silicon-oxygen tetrahedrons in the C-S-H gel, but also the hydration reaction speed of cement paste at this stage. This viewpoint was confirmed by the experiment for the samples with added superplasticizer. The shifting characteristics of the absorption peaks in the range 800-1 025 cm^-1 for the samples at the ages of 8-12 h were comprehensively investigated in this study. The research results show that the shifting speed of the characteristic peak for the blank sample is exactly the same as that for the sample reinforced with CNTs. Therefore, addition of CNTs materials into Portland cement doesn't influence the hydration reaction at the early age. This conclusion is verified by the calorimetry test for hydration temperature.