Because of the lower cost and easier construction operation, soil-nailing wall has been widely used for foundation retaining and protection project, which brought great economic profits accompanied with more and more designing and construction experience. But the blind application of soil-nailing wall may bring safety-hidden danger to foundation pit engineering. By the case of foundation pit side-slope collapsing accident in Haikou, the analysis on the accident cause was made with treatment measures put forward. Some suggestions for the design and construction were presented to avoid the similar accidents of foundation pit engineering.