The aim of this paper is to improve the performance of the non-linear eddy viscosity model for simulating the wind flow around the building. Firstly, the state of art of the predicting wind flow around building using RANS model was introduced, and the problems in the simulation were analyzed. Then an improved non-linear eddy viscosity for predicting the wind flow around buildings was proposed based on Craft model. The improved non-linear eddy viscosity was validated and analyzed through the wind tunnel data provided by AIJ. The results showed that the proposed non-linear eddy viscosity improved the overestimation of turbulent kinetic energy in impingement region by the standard k-ε model, and predicted better results in the wake region behind buildings simultaneously through strengthening the eddy viscosity in the wake region. After the improvement, the non-linear eddy viscosity model can predict the wind environment around buildings better.