This article describes gyro fault diagnosis architecture in satellite attitude control systems and designs two H∞ optimal fault observers by dint of Takagi-Sugeno(TS) fuzzy model in the case that the premise variables are known or not.Sufficient conditions for the existence of the two H∞ optimal fault observers are derived respectively.Mathematical simulation is carried out to validate the effectiveness of the fault diagnosis method.Performance and practicability properties of the H∞ fault observers are analyzed synthetically.