Crystalline efflorescence was found on some eaves tiles collection in National Museum of China. In order to recognize the composition of the salts, some sample was collected from one piece of eaves tile. 3D video microscope and scanning electron microscopy were applied to observe its morphology, the crystalline salt included yellow-white powder and white fibrous crystals. Raman spectroscopy, infrared spectroscopy and X-ray diffraction were used to identify the two kinds of salts. According to the mutual confirmation of different spectral analysis results, the main composition of yellow-white powder was calcium carbonate, while the main composition of fibrous crystals was thecotrichite. Thecotrichite is an efflorescent salt occurring on surfaces of porous calcareous objects stored in wooden cabinets. Those wooden cabinets are easily emitting amounts of acetic acid vapor. Therefore, it is recommended that the eaves tile be removed from the wooden cabinet, desalinated, and stored in an acid-free environment. The spectroscopic method can provide technical support for identification of ancient pottery crystal salt composition. The results provide scientific data guidance for the establishment of the conservation and rehabilitation programme.