Abstract: As a technique for protection of adjacent buildings, the outrigger-type diaphragm wall been applied in deep excavation engineering. But the worldwide researches in this area are still relatively scarce until now. In extension project of Hangzhou Huanglong Hotel, outrigger-type diaphragm walls are adopted to solve the problem of insufficient rock-socketed depth. And thus the rock-socketed depth of support structures in intermediary weathered rock is ensured. Moreover, the construction difficulty is reduced. Good social and economic benefits are gained. Based on the Huanglong excavation case, a 3-D finite element model is presented to simulate the behavior of outrigger-type diaphragm walls by using the software ABAQUS. The behavior of soil is assumed to conform to the modified Cam-clay model, and the actual construction sequence is simulated. The numerical results and monitoring data in the excavation of lateral displacement are compared. The reasonable stiffness of the section steel in the outrigger-type diaphragm walls is also analyzed.