Clinical Chinese Medicine commonly used gypsum (CaSO4·2H2O) to treat febrile diseases. Based on the study of microscopic crystal characteristics and trace element characteristics of gypsum, the hypothesis that trace element strontium (Sr) is an important influential element for gypsum cooling is proposed. We analyzed the microscopic crystal structure and trace element composition of 33 batches of gypsum herbs from five producing areas by optical polarized light microscopy (OPLM), X-ray diffraction (XRD), electron probe micro-analysis (EPMA) and inductively coupled plasma mass spectrometry (ICP-MS). The results of OPLM analysis show that the microscopic morphology of gypsum is mainly long columnar and fibrous, and is related to the original area of gypsum. According to the traditional requirements, the samples with good quality have larger micro-particles. XRD analysis showed that except for one batch of samples containing quartz impurities, the other samples showed no other mineral impurities. The results of EPMA analysis showed that the main mineral in the gypsum sample was gypsum and the secondary mineral was anhydrite, which showed a symbiotic relationship. The anhydrite in the micro-area image has no definite crystal form, and the contact surfaces of anhydrite and gypsum are irregular curves. It is speculated that the anhydrite is converted from the gypsumin the later stage of mineralization rather than native. The results of ICP-MS analysis showed that the trace element strontium (Sr) was higher in gypsum, and the highest absolute content of all trace elements. The comparison with trace elements in the primitive mantle showed that the Sr element is the most stable and enriched trace element in the gypsum sample, which is more than 6 times more than the primitive mantle, up to 176 times. The analysis of the value of CaO/SrO in the micro-site of gypsum shows that the strontium (Sr) element is statistically uniformly distributed in the gypsum and exists mainly in the form of isomorphic mixtures in gypsum. The results of the determination of the Sr element content in the aqueous gypsum solution showed that the dissolution amount of strontium (Sr) in the gypsum decocted fluid and the gypsum suspension reached 2～4 times of the theoretical value. Gypsum was used in large doses in the clinic, and decocted first can promote the dissolution of Sr2+. Because Sr has the effect of inhibiting Na. The hypothesis of gypsum cooling: when gypsum is used for cooling, Sr2+ and Ca2+ are simultaneously dissolved. Sr2+ inhibits the absorption of Na+ to the body, increases the supply of Ca2+ to the body, and regulates the ratio of Na+/Ca2+ one of the positive regulation medium of fever. The material basis for the cooling of gypsum is the joint action of Sr and Ca.