It is a general way to construct expressway interchanges by stages. The engineering construction cost, road network operational efficiency, and operational security are directly affected by the rationality of the scheme design. Considering the features of short-term and long-term integrated design of interchange, the necessity of research on design ideas was analyzed. Two short-term and long-term integrated design principles were defined, and their applicable conditions, advantages and disadvantages were analyzed. The main control factors of design principles were thus determined. With the main control factors as the criterion and design principle as the goal, the analytic hierarchy process (AHP) was employed to construct the short-term and long-term integrated design idea of interchange. This idea was applied to the scheme research and decision-making of the Yisong interchange on the Ninglang?Shangri-La expressway, which verifies the effectiveness and rationality of the design idea and can provide a reference for similar interchange scheme design.