This paper analyzes the influence of building openings on the natural ventilation performance and the building energy consumption. The software Airpak and the building energy consumption simulation software DesignBuilder are used in the simulation. The influences of the building's orientation and the opening's position on the natural ventilation performance and the building's energy consumption are analyzed according to the Changsha typical meteorological data. A new evaluation index is proposed to compare the design schemes with consideration of the performance of the natural ventilation and the building's energy consumption. The optimal scheme combination of the building's orientation and the opening's position is obtained by the index.