Abstract: According to the principles of thermal economical science, by analyzing the total expense of double insulating pipeline, at the same time by considering the national standards of thermal insulation and situation of engineering practice, an optimal mathematical model of overall design for double insulating pipeline was set up and solved by programming. The deduced model and corresponding software can be applied to the design of surface or underground pipelines of single phase or multiphase fluid. They can help designers to determine optimal pipe diameter and economical thickness, which can increase their design efficiency and quality.