Abstract: Spectrum analyzers are key instruments widely used in radio electronics. The long-term stability of their critical parameters has been a significant concern for users and manufacturers. Accurate tracking of technical specifications plays a crucial role in the research, development, improvement, usage, and maintenance of these instruments. The National Institute of Metrology has accumulated calibration data for spectrum analyzers spanning over a decade. These metrological scientific data are characterized by traceability and accuracy. Based on these data, this paper introduces the operational principles, key performance specifications, and measurement calibration systems and methods of spectrum analyzers. It focuses on analyzing variations in the displayed average noise level and input frequency response during long-term usage of typical spectrum analyzers among representative domestic users. This study aims to provide a more reliable basis for the development, production, testing, and maintenance of spectrum analyzers.