Abstract: Thermal instruments can monitor the parameters such as pressure, temperature, flow and vibration during the operation of power plant equipment, so as to find abnormalities in time. While preventing safety accidents, realize the economic operation of equipment. However, the operation environment of thermal instruments in power plants is poor, and there are many influencing factors, which are prone to various faults and problems, affecting the effective play of the functions of the instruments themselves. In this regard, technicians should analyze the common faults of thermal instruments. For different thermal instruments such as pressure measuring instruments, temperature measuring instruments and flow measuring instruments will produce different faults in operation, correct treatment methods are given, and effective solutions are taken to improve the reliability of thermal instruments, so as to provide guarantee for the safe operation of power plant equipment.