In order to protect and reinforce the Najing City wall, various conservation methods and reinforcement techniques were explored on the geological character of Shizi Mountain and architectural features of the wall. In addition, the damaged wall was investigated and the mountain body was explored in order to understand the reasons for the partial collapse of the Shizi Mountain part of the Nanjing City wall. Through the use of traditional techniques and modern reinforcement, the damaged wall, the drainage system was restored between the wall and the mountain, a system was set up for monitoring cracks in the wall, and the wall’s overall survivability was improved. This work can serve as a technical reference for similar projects.