Abstract: The environmental barrier coatings (EBCs) deposited on SiC/SiC composites can prevent or retard the corrosion of subsmate material and prolong the life of the SiC/SiC composites. The EBCs are easy to fail because they are made by brittle ceramic materials and their service temperature is high. The failure mechanism research of EBCs exists in the development progress of materials system, and which is associated with the service environments. This article summarized the EBCs' mechanism during high temperature oxidation, thermal impact and H₂O-O₂ service environments. The results show that the EBCs failure is related to the stability of each coating, and is affected by the compatibility between the coatings. Then it is suggested that the reactions between the coatings should be paid attention.