Based on the theory of the current economic evaluation of the highway construction projects, the author makes clear and demonstrates the computer program processing and the principle of designing the models of the Economic Evaluation System of the Highway Construction Projects in this paper, and concisely introduces the clew to design the system, the constitutes and functions of the system and the key technology. Finally, the author designs the computer implementation program taking the computation of economic evaluation internal returns ratio target as the example, and carries on the confirmation by the project example computation.