OBJECTIVE: To determine the composition, structure, trace elements and thermal stability of Tibetan medicine Nanhanshuishi.METHOD: The trace elements, the structure, and the thermal stability of Nanhanshuishi were assayed and calculated by X-ray fluorescence spectrometry (XRF), inductively coupled plasma optical emission spectrometer (ICP-OES), atomic fluorescence spectrometry (AFS), inductively coupled plasma mass spectrometry (ICP-MS), X-ray power diffraction (XRD), TG-DTA. RESULT: The results indicated that the phase is mainly made up of CaCO3 (Rhombohedral, R-3c) in Nanhanshuishi. The analysis of elements show that Nanhanshuishi is rich in Ca and O, and contains other more than 20 minor elements, such as Si, Mg, Fe, Al, Na, K, Zn, Mn, Pb, As, Hg etc. The result of TG-DTA show that the weight of Nanhanshuishi starts to decline from near 700 degrees C and get steady above 850 degrees C. CONCLUSION: The study provided scientific data for the establishment of quality standards of Tibetan medicine Nanhanshuishi.