Recently there has been a lot of attention to fibers and fabrics which have the quality to adapt themselves to their surrounding climate. We can acquire this quality using Phase Change Materials. Phase Change Materials theoretically can be changed in to another form in constant temperature and consequently can save a large amount of energy. These materials include two clusters: organic and inorganic. Inorganic materials are good materials to be used for saving thermal energy; because they have high capacity per volume, high thermal Conductivity and they are low priced. Anyhow, there will be some problems in using hydrated salts as Phase Change Materials, one of these problems is phase separation and the other is subcooling. These problems will reduce thermal capacity, immensely and cause inconstancy in thermal properties of hydrated salt. In this research we used Na2SO 4 .10H 2 O and an Eutectic mixture of Na 2 HPO 4 .12H 2 O and Na 2 CO 3 .10H 2 O as inorganic Phase Change Materials in fabric structure for the first time. These inorganic Phase Change Materials melt around body temperature. In this research we introduce a simple method to keep inorganic Phase Change Materials in fabric structure. By this method there is not necessary for Phase Change Materials to be micro capsulated. We used coating technique for preparation of fabric containing Phase Change Materials. Thermo physical properties and thermal stability effect of treated fabric was checked out by Differential Scanning Calorimetry and Thermo Gravimetric analysis. Fourier transform infrared spectroscopy (FT-IR) was used to determine the chemical structure of fabric with Phase Change Materials. The air transfer, water permeability, and physical properties of treated fabric were also investigated. The results show that adding Nano Montmorillonit as thickening agent and Sodium tetra borate as nucleating agent to Gluber's salt cause the system to be stable thermodynamically and could be used in various thermal cycles without reducing thermal capacity. In this research، considering the repeatability of thermo physical qualities of fabric with inorganic Phase Change Materials, it can be said that subcooling and phase separation problems are completely eliminated . FT-IR analysis indicated that there was no chemical interaction between materials in silicon rubber matrix. Investigation of textile physical properties shows that the thickness and bending properties of treated fabric did not change significantly and it is because of the elastomeric structure of silicon rubber. The air transfer and water permeability of fabric were reduced generally but, the water permeability of treated fabric was tolerable. As a result, Silicon rubber can be applied on textile structure to hold Phase Change Materials while there is no need for Phase Change Materials to be microencapsulated and treated textile can be served as an appropriate smart thermal insulator. Keywords : Inorganic Phase Change Materials, Thermal energy storage, smart textile, inorganic nanoparticles, thermal properties stability