In recent years, expressway reconstruction and expansion projects have been increasing, and expansions from four to eight lanes and from six to ten lanes are relatively common. In the design process of reconstruction and expansion, the rationality of the design for overlay, widening, and lap treatment of “white-to-black” pavement has a significant impact on pavement reconstruction quality. The formation of ultra-wide pavement after reconstruction, especially in sections such as acceleration and deceleration lanes, areas with small composite longitudinal slopes, and the bottom of concave curves, makes pavement drainage difficult, which affects driving safety to some extent. Meanwhile, milling waste generated during pavement reconstruction should be fully recycled to save costs and reduce environmental pollution. Stone materials generated from tunnel excavation are often discarded or only used for subgrade filling, causing resource waste; they can be fully utilized in structural layers of pavement. Based on the practical achievements of the Shenshan West Expressway reconstruction and expansion project, key technologies for the overlay, widening, and lap treatment design of “white-to-black” pavement, drainage design for ultra-wide pavement, waste recycling, and utilization of tunnel slag were proposed in this paper. Currently, the Shenshan West Expressway reconstruction and expansion project has been completed and accepted for two years, and the overall pavement performance is excellent, which indicates that the adopted key technologies for pavement design in the reconstruction and expansion project are feasible.