The technical specifications of nuclear power plants are important license documents followed by the operation of nuclear power plants. Technical specifications specify a Limiting Condition for Operation (LCO) of the containment air average temperature that must be met. Because of the large free volume of containment and the existence of multiple compartments, the heat input of different compartments is different, which leads to a large discrepancy in temperature. This paper discusses the determination of containment air average temperature LCO and how to realize the measurement and display of containment air average temperature during normal operation, so that average temperature of containment can be supervised timely and the LCO will be satisfied. And when LCO deviation occurs, timely measures should be taken to restore containment air average temperature to ensure that the containment operates within the assumed range of accident analysis, ensuring the effectiveness of the third safety barrier and preventing radioactive releases.