With the continuous development of urban construction, the underground structures are becoming increasingly complex. To alleviate the traffic congestion and ensure the safety of pedestrians crossing the street, the long-span footbridge is more and more widely used. How to balance the bridge design principles and construction constraints has become an inevitable problem in the design of urban footbridge. For this purpose, relying on the design project of a long-span steel truss footbridge in Guangzhou, the structural design, the structural calculation, and the influence on subway operation of the bridge are set forth and analyzed. The analysis content can offer references for similar projects in the future.