Abstract: In order to economize space and enhance space utilization, shared walls are sometimes employed in buildings. During the renovation process of old buildings, when adjacent buildings are demolished, shared walls often encounter the current situation of material aging and wall failure. As most old renovation projects are simultaneously situated in environments with inconvenient transportation and the absence of auxiliary hoisting machinery, there are considerable problems in terms of construction efficiency, positioning, and installation accuracy control for the overall reinforcement of old shared walls. To shorten the construction period and guarantee the installation accuracy and quality, this paper takes the upgrading and renovation project of Guangzhou Restaurant on Wenchang Road as an example, analyzes the key points and difficulties of the protection construction of old shared walls under the condition of soft stratum, proposes the foundation construction technology for the protection of shared walls under the condition of soft soil layer and the protection technology of shared walls by converting the original structural system, and conducts research on the new node between the added steel column and the original concrete beam. The project effect inspection indicates that after adopting this construction technology, the construction period can be shortened by 24% and the cost can be saved by 20%. This construction technology can offer experience reference and certain referential significance for the protection construction of old shared walls under similar conditions of soft soil layer.