Temperature and relative humidity are both significant indicators of the museum environment. Based on the criterion of stability and appropriateness, a new approach to evaluate museum environment is presented. By calculating the dispersion level of monitoring data away from a set point and assessing its level of distribution, the environmental quality of temperature and relative humidity in a museum environment can be determined, in addition to the longterm trends and seasonal fluctuations. The monitoring data collected in the Sichuan Museum from 12 different galleries and storage areas in 2014 were used to evaluate the effectiveness of the model, which proved to be reasonable. The method provided data for control of museum environment and design specific preservation conditions for relics in the museum.