Abstract: Grotto temples are a type of Buddhist relic carved into cliffs. Influenced by the engineering geological environment, grotto temples in various regions face different degrees of deterioration and instability. A zoning scheme consisting of four major zones and nine subzones for the engineering geological environment of grotto temples was proposed in this paper, based on the characteristics of climate, geomorphology, hydrology, and active tectonics in China. On this basis, the relationship between these factors and the deterioration and instability of grotto temples was analyzed, and their impacts on grotto temples were quantified using the analytic hierarchy process. The results indicate that grotto temples in China are primarily concentrated in the Tianshan Mountains region, the Altun Mountains-Hexi Corridor region, the Ordos Plateau region, the Lvliang-Taihang Mountain region, and the Sichuan Basin region. The quantity of grotto temple relics in these areas accounts for about 58% of the total in China. The issues of grotto deterioration and instability can be divided into two major categories, eight types of diseases, and four external influencing factors. Additionally, the regional nature of the deterioration and instability of grottoes is controlled by the frequency and degree of development of engineering geological disasters and the diseases of the cultural relics themselves. Among the four major zones, active tectonics and climate are the primary controlling factors for the deterioration and instability of grotto temples, with their maximum weights reaching 0.53 and 0.37, respectively. In contrast, geomorphology and hydrology have a more balanced and lower influence in each region. This study can provide basic support for the preventive conservation, stability monitoring, and reinforcement technology research and development of grotto temples.