The application of post-tensioned prestressed concrete small box beams in the new construction of S3 Highway Project (Zhoudeng Highway - G1503 Highway Lianggang Avenue Interchange) is introduced. The advantages of the small box beam are compared with the other structures. The application and optimization of the structures and sections in the project are described. The calculation parameters and stress control of small box beam are briefly introduced. The application of simple-supported to continuous small box beam in the small-radius interchange is introduced. The problems are required for attention in construction of small box beam.