Abstract: Herein,we addressed the design of energy saving window of apartment building in Ordos region.The heat-flow through window was mathematically modeled by trial-and-error and numerically simulated with DeST software.The influence of the realistic situations,including but not limited to the climate,size/orientation/material/structure of window,window-wall ratio and air-conditioning cost,on the energy consumption per usable floor-area was investigated.Moreover,the window materials and structures were selected in analytic hierarchy process(AHP).The simulated results show that the window material/orientation/structure and window-wall ratio all have a major impact.For example,when it comes to energy saving window,the high-tech materials,including the frame of steel reinforced polyvinyl chloride(PVC),double/triple glazing(insulating) glasses and Low-e glass,make all the difference.We suggest that the simulated results be of some technological interest in design of window in cold and extreme cold regions.