## 3 Index System
### Construction of Index System  
(1) Construction method:  
An analytic hierarchical process (AHP) was proposed by American operations researcher [PERSON] in the 1970s [31]. The AHP is not only scientific and reasonable in theory, but also simple and easy to apply. It can comprehensively analyze qualitative and quantitative problems. It is a decision-making method suitable for multi-objective decision-making. Its purpose is to address the complexity and subjectivity of decision problems. (2) Construction steps  
Using the transformation of old industrial buildings into sports venues as the research object and adhering to the relevant principles (such as scientificity, systematicness, operability, and mutual exclusion) to establish evaluation index systems, system construction was completed by referring to the guidelines on the recycling of old industrial buildings, the design specifications of sports buildings, and the relevant standards for the recycling of old industrial buildings [32; 33; 34; 35]. The specific steps are as follows:  
Step 1: Establishing the initial hierarchical structural model  
Based on field research, expert guidance, and a literature analysis [37; 38; 39], the structure initially established 5 dimensions for first-level indicators, and 28 for second-level indicators. Index analysis:  
The primary considerations when converting an old industrial building into a stadium are safety and structural stability. The stadium needs to be able to withstand the load of a large number of spectators and participants, so the building structure must be strong and stable enough. The feasibility of the site layout and other facilities is inseparable from the structure of the building, and some old industrial buildings may have outdated structural designs with which it is difficult to meet the requirements of modern sustainable architecture. Therefore, evaluation of the structural condition of old industrial buildings helps to determine the technical options, budget, feasibility, and environmental impact of the renovation process, and ensure the successful implementation of the renovation project. The importance of location advantage for the transformation of old industrial buildings into stadiums lies in the provision of good accessibility and the convenience of surrounding facilities and services. A good location has a high degree of commercial activity and will attract more consumers and business cooperation. The right location is the key to ensure the successful operation and sustainable development of the project. Reasonable planning and design can make full use of existing resources to reduce the cost of projects and reduce the impact on the environment. The efficient use of this resource is a key factor in economic efficiency, alongside assessing renovation costs and construction periods, determining the feasibility and cost budget of the project, and determining whether there is an economic advantage to transformation compared to the construction of a new stadium. During the renovation process, meeting the needs of people for cultural and sporting activities and improving the living environment can help to achieve the sustainable development goals, protect the historical value of the building, and promote the development of creative industries. It is a social element that needs comprehensive consideration. To summarize, reasonable index evaluation can improve the suitability of old industrial buildings to be transformed into sports venues. Step 2: Consistency check  
To ensure the feasibility of each index, the importance, correlation, and discreteness of the indices are analyzed based on the statistical analysis software Statistical Product and Service Solutions (IBM SPSS Statistics 26) (As shown in Tables 1 and 2).