The old retaining wall repair problems are encountered in the Water Quality Improvement Project in Shenzhen. This paper summarizes the commonly used retaining wall repair process and repair methods in the project. Firstly, the testing company is required to investigate the current situation of the retaining wall and find out the potential safety hazards. The appearance survey, geophysical detection and other comprehensive means are used to analyze the hidden danger points, so as to evaluate the quality of the retaining wall project and give suggestions for the repair of the retaining wall. Then, it is recommended to demolish and reconstruct the ecological retaining wall with conditions for implementation after detection ; For the recommended repair of old retaining wall, Soil Nailing Hanging Panel Scheme and ' L ' Type Pile Wall Combination Scheme are commonly used. At the same time, different repair schemes should be adopted for different retaining wall defects, such as the crack defect repair scheme in this paper, which saves investment and achieves good repair effect.