As an outstanding cultural heritage with both esthetic and historical significance, as well as a key component of Chinese classical gardens, rockeries are an extremely important cultural heritage that could be affected by a variety of man-made and natural factors; thus, a comprehensive and detailed assessment of their structural conditions is necessary. Structural risk, as both the most significant and most influential type of risk facing rockeries, could have a devastating impact on rockeries. However, previous studies have not considered the development of systemic structural diagnostic tools for rockeries. Therefore, to diagnose structural conditions by obtaining objective indicators that enable an efficient comparison between different rockeries, this study proposes a structural risk assessment tool to calculate the structural risk index for rockeries in Chinese classical gardens. This method was developed based on the MIVES model, which is a multi-criteria decision-making process founded on the concept of value function. The proposed method emphasizes a detailed diagnosis of the structural conditions of rockeries based on objective data and scientific force analysis. Compared to the health risk assessment method developed for rockeries in Chinese classical gardens in previous studies, this method represents a more detailed step toward assessing the structural condition of rockeries. Once the initial health risk of a rockery has been determined, a structural risk assessment should be carried out for those with a high-risk rating so that their structural condition can be evaluated and a more targeted response strategy can be adopted. The application of this method to four case studies demonstrated its usefulness.