The quality of social relationships is recognized as an important aspect of human well-being. Improving social relationships can help to promote other aspects of human well-being, such as health and income. The development of individual social relationships relies on regional social relationships. However, few studies have focused on social relationships evaluation at the regional level. Therefore, the study aims to construct a comprehensive evaluation index system and to evaluate regional social relationships by calculating the regional social relationships index (RSRI). The weights of the indicators were calculated by using the analytic hierarchy process (AHP) and entropy weight method. The social relationships of prefecture-level cities in the Qinghai–Tibet Plateau were evaluated based on statistical data. The results showed that (1) the top three indicators of comprehensive weight were number of community service agencies, number of vehicles operated on highway, and telephone penetration; (2) the regional social relationships on the Qinghai–Tibet Plateau showed an upward trend from 2010 to 2019; (3) the average RSRI scores of prefecture-level cities in Qinghai and Gansu were higher than other provinces; and (4) the number of community service agencies was the main obstacle factor for the development of regional social relationships in the Qinghai–Tibet Plateau. The finding of this study can provide further insights about social relationships research from a regional analysis perspective and cover the gap in the literature on regional social relationships.