Abstarct: Modern societies today, have intense dependence on industrial systems and update technology and there are probabilities of fault occuring in these systems and creation physical and financial loss. Actuator fault lead to reducing operation control system and sometime impairment complete in system. Sensor fault lead to not appearing actual amount in process and is far away from its work point. In this stage, subject related to safety, exploiting, economic exploiting from system and industrial equipments have significant role. There for identification fault and isolation in systems that used by industries, are anavoidable. In this thesis, we discussed about fault and its type and we defined brief history from ideas and theories that are presented by different researchers in this field then we attextion to advantages and advances up to now used in observer design in sliding mode, identification and fault estimation in sensor control system. In following , we using two method ؛ observer sliding mode and observer sliding mode baxsed on logic fuzzy for identification and fault estimation in inverted pendulum system and with stimulations in their power and qualities , show identification and reconstructions sensor fault.