The main objective of this book is to control indoor temperature and reject faults tolerant like sensor deterioration, noise, disturbance and depreciation of the plant in building air conditioning system; we propose a fault tolerant controller system (FTCS) strategy for temperature control of air-conditioning system. The set-point response controller in the FTCS is designed in terms of insusceptible with noise, failure sensor, disturbance and parameter variation with optimal performance specification. The output of system was predicted through indoor, outdoor disturbance, at last based on the mathematical model of air-conditioning space. According to the system operation requirement for faults rejection, a closed-loop for rejecting faults signals is configured. It is found that the set-point response, the disturbance rejection, the noise rejection, the robust, rejection of failure sensor and the performance of the designed FTCS are better. Therefore the residual signal can now be used to monitor faults in the system while the proposed method ensures correctness of operation. Furthermore, FTCS has achieved the desired indoor temperature, superior performance, adaptation, robustness.