Terahertz (THz) spectra for different palm leaves are measured by Fourier transformed infrared spectroscopy-attenuated total reflection, and the physical morphologies and chemical compositions of the leaves are characterized by scanning electron microscopy and infrared spectroscopy, respectively. Accordingly, the THz fingerprint peaks of chlorophyll and carotenoid are experimentally identified. In addition, the results indicate that the influence of the chemical composition in plant leave on optical response is significantly stronger than that of the physical morphology. Moreover, among the main chemical components of palm leave, the THz response of chlorophyll is stronger than that of carotenoid. In this work, new methods of investigating the optical properties of the planes and of developing novel THz sensitive organic materials are also proposed. Particularly, some important results are reported for the first time in this article. These valuable results will be helpful not only for an in-depth understanding of the physiological behavior of the plants, but also for the obtaining of inspiration for designing functional materials of device with higher performance, higher pertinency and wider applications, and thus promoting the development of related theories and applications.