This paper discusses the mechanism of protection against oxidation of coated materials at elevated temperature.The high temperature processon interface between coating and substrate is as follows,oxygen diffuses through coating onto substrate,then it results in oxidation of alloy elements. The performance of coating is to reduce diffusion of oxidizing atmosphere, thus it also reduce pauperization of Cu,but it is out of function for Ti and Al. Besides,there is small amount of Si to permeate into substrate,its thickness is about 0.2mm after duration of 1000hrs at 1100℃. Besides oxidation,no other resultant of reaction has been found along interface between coating and substrate.