Wind is an available main form of renewable energy. Following the development of installed capacity growth in China, an improvement is needed in wind resource assessment and wind power forecasting techniques. Numerous studies on the numerical simulation of complex terrain flow fields have been conducted worldwide. With the increasing capacity of numerical calculation, Computational Fluid Dynamics (CFD) models have been used in the meteorological field and are coupled with mesosacle models to simulate the flow fields on complex terrains. In this paper, a coupled model system for wind resource assessment was studied. In this study, a mesoscale meteorological model, the Weather Research and Forecasting (WRF) model, was used to downscale data from the global scale to the inner nested grid scale of a few kilometers and was then coupled with the Fluent method. High-resolution results of wind speed distribution data and refined wind farm information were obtained. The refined WRF/Fluent system was then applied to the complex terrain flow field of the Poyang Lake region and Yangmeishan in Yunnan. The results showed that this approach is viable for the assessment and forecasting of wind energy.