To preserve precious relics and to eliminate or slow down aging, it is necessary to monitor, evaluate and control the microclimatic in museums. Temperature and humidity are two of the most important factors. Temperature and humidity in museum environment need to be appropriate and stable. This paper discusses the methodology for long - term temperature and humidity evaluation in museum environments. Conventional evaluation methods are compared. To assess appropriateness, the temperature and humidity qualification percentage and distribution map of temperature and humidity were proposed. To assess stability, an index of variation of temperature and humidity was established. As an example, monitoring data of the temperature and humidity over a period of 8 months in a museum exhibition hall were evaluated. It has been shown that these methods are effective.