Night ventilation has been proved to be an effective cooling method, especially in regions with a large temperature difference between day and night. The main work of this paper is to analyze the parameters associated with ventilation effects in office buildings with night ventilation in the city of Xi'an. For this purpose, field investigation about different kinds of office buildings has been carried out, based on which, a typical office building simulation model has been built. Three parameters, including temperature difference between day and night, thermal storage performance and air change rate are studied by the energy simulation software DeST and the optimum values have been proposed for each parameter. The conclusions can be useful in night ventilation design process.