Hydrous minerals play an important role in transporting and storing of water in the deep Earth. The study of physical and chemical properties of hydrous minerals is important to understand the mode of existence of water, the mineral composition and structural behavior in the subduction zone, and also can help us properly understand the subduction dynamics. Epidote-group minerals are common hydrothermal alteration minerals in the basalt and one of the major hydrous minerals and an important carrier of water in the Earth’s interior. Therefore, the studies on the structure and thermoelastic properties of the epidote-group minerals have great significance in geology. The author have studied the PV/VT/PVT equation of state (EoS) of epidote, clinozoisite and zoisite by using external resistance heating diamond anvil cell combined with synchrotron radiation power X-ray diffraction method and Raman spectroscopy. Combined with previous studies, we discussed the effect of the isomorphous substitution on the unit-cell volume, bulk modulus and other physical parameters in epidote-group mineral. The experimental results suggest that:1. By analyzing the PV EoS of epidote and clinozoisite, we found that the bulk modulus of epidote-clinozoisite solid solution decreases with the increasing composition of iron. The possible reason for this phenomenon is that the radii of Fe3+ cation (0.645 ?) is bigger than Al3+ cation (0.535 ?), the volume of MO6 octahedron increases with increasing radii of M3+, and then more easy to be compressed. In the zoisite-clinozoisite homogenous two-phase variants, is the bulk modlus has no linear correlation with the composition of iron. In addition, the zoisite is easier to be compressed than clinozoisite.2. Researching for epidote VT EoS at high temperature gets the coefficient of thermal expansion (α0). In addition, according to the PVT EoS of epidote, we also obtained the temperature derivative of the bulk modulus (dK/dT)P and thermalexpansivity coefficient (α0) of epidote. Comparing the two experimental results, we found that the thermal expansivity coefficient (α0) at simultaneously high pressure and high temperature is obviously larger than the value obtained at high temperature.3. We also completed the high pressure Raman spectroscopy studies on epidote and clinozoisite. With increasing pressure, the pressure coefficient of M-O modes and Si-O modes in epidote is obviously larger than clinozoisite, which can also prove the conclusion that epidote is easier to be compressed than clinozoisite.4. Using the EoS data in this study combined the EoS experimental results of other hydrous minerals from previous studies to calculate the densities of epidote, zoisite, clinozoisite, brucite, serpentine and chlorite under different geothermal gradient in subduction zone. And then, it is presumed that epidote with higher iron content contribute to subduction plate into deep mantle.