Abstract: Based on a typical case, the optimal design for the collapsed excavations is performed. The principle of the optimal design is that the displacement is controlled according to the modulus of soil, while the soil pressure is controlled according to the cohesion and friction of soil. Based on this principle, the problem that the soil pressure inside and outside the pit are unequal after backfilling is addressed. Moreover, the typical sections of the pit are calculated by the software for supporting structures of deep excavations. The calculated results are compared with those by the traditional methods and the finite element method, which proves the reliability of the optimal design. The proposed method will give guidance for other similar projects.