The project is located at the intersection of ecological street and South Fourth Ring Road in Changchun. Bid section D1 is an interchange. The East longitudinal main line crosses the ecological square roundabout, Shirong Road, Shiguang road and xiaoheyanzi River from south to north. The fourth ring main line is interconnected with the East longitudinal main line through ramps. (60 + 80 + 60) m variable height steel box girder is used in this project. The height of the box girder changes according to the quadratic parabola, and the width of the steel box girder is 34.06m ~ 24.76m. Maximum section: 5.0m.