Abstract: A discrete three dimensional(3 D) finite element model(FEM) has been developed for the analysis of soil nailed structures.The soil constitutive law is chosen to analogize the behaviors of soil during excavation.The tensions of nails and their adhere slip behaviors are simulated by bar elements and two note double spring elements,respectively.The staged excavation and retaining can also be simulated in this model.The working principle and strain stress performances of soil nailing are researched.Parametric studies are applied to examine the effects of several factors on the deformation.An engineering case is,as an example,analyzed and the predicted soil deflections are compared with those measured in situ and computed by the existing 2 D FEM.The 3 D FEM obtains better results than the 2 D FEM.Conclusions may be of very high practical value in design and construction of soil nailing.