The geological conditions were analyzed for the foundation pit engineering of Passenger Car Institute of First Automobile Group in Changchun, the analysis and demonstration were made on the supporting scheme and the soil nailing wall support scheme was designed. The optimal design of soil nail inclination angle was made within a reasonable range with single factor analysis method and the influence law of soil nail inclination angle on foundation pit slope stability was obtained. The practice shows that by this soil nailing wall supporting scheme, the engineering works was completed with short-term efficiency and investment saving; by the optimization design of soil nail inclination angle, the construction safety was greatly promoted with original project construction cost. This practice provides conference to the application study on soil nailing wall support of foundation pit engineering in Changchun.