Abstract: The current design concept of pile-anchor and soil nailing wall composite support structure is to separate pile-anchor and soil nailing wall and to design each of them independently. According to this design concept and the actual construction process of composite support structure, three different numerical simulation models are constructed separately for the upper soil nailing wall, the pile-anchor structure under the upper soil nailing wall and the whole composite support structure. Through numerical simulations of different designing methods for the structure, the following results are found: the composite simulation method can consider both the upper soil nailing wall and the pile-anchor structure in the same time, and satisfies the actual construction process so that its results are more reasonable; compared with the results of the composite simulation method, in the single simulation model for soil nailing wall the horizontal displacement, subsidence and axial force of soil nails are more less, if support design is based on these results the soil nailing wall will be insecure; on the contrary in the single simulation for pile-anchor support structure the magnitudes of anchor forces, subsidence and moment of pile are bigger than the results of composite simulation. Thus the single design for pile -anchor structure will make the support conservative.