Soil nailing is a popular reinforcement method for stabilizing slopes, excavations, and retaining walls in many countries. The pullout capacity of the soil-nail interface is a critical parameter for the design and safety assessment of soil-nailed systems. In this paper, a three-dimensional (3D) finite element (FE) model is developed using the commercial program ABAQUS to simulate the pullout test of a soil nail in a soil-nail pullout box. The stress-strain behavior of the soil and soil-nail interface is described by a Mohr-coulomb model and coulomb friction model respectively. A novel temperature-based reduction of friction coefficient has been applied in order to reduce the roughness of soil-nail interface as the slip occurs. Validation of the FE model is carried out by comparing the results of numerical simulations with experimental data from a previous work. The comparisons between the modeling results and experimental data have demonstrated that the established FE model can simulate the pullout behavior of a soil nail in a soil mass properly. Based on this, the verified FE model has been used to investigate the effect of different nail diameters, soil elasticity moduli and pullout rates on the pullout behavior of the soil nail.