This article is a comparative evaluation of airflow in two kinds of Yazdi and Kermani Wind-Towers. In the late decades of twenty century regarding to high population growth rate and energy crisis, vernacular architecture and its passive methods for gaining thermal comfort, has been strongly focused. Moreover, a huge scientific movement setup for researches deep in exploring passive cooling and heating methods, and subsequently translating these methods in to contemporary architecture. In addition, Iran as one of the populated countries of the region with a high consumption rate and concerning its glorious architecture history is no exception too. Wind tower has known as one of efficient climatic features of Iranian traditional architecture in hot arid climate. This element had an important role in regulation of air temperature in traditional housing. Using domain of wind tower is limited to temperature Middle East, including Iran, some Arabic countries, and some African countries either. Totally, performances of wind towers are air conditioning and air vacuum, cooling nutrition and preventing of putrefaction of water in water storages. In wind towers in one direction the funnel of air occurs and in behind direction because of negative pressure and air vacuum, proper air will be flew into tower and internal hot air comes out. This article is an innovative study because of its attitude to airflow impact on wind tower structure and efficiency. This paper is an attempt to evaluating two kind of wind-towers to discussion the two main questions: 1. What is the role of Orientation of wind-towers span, regarding to climate and its height, in two kinds of Kermani and Yazdi wind-towers. 2. Which one of these two has better performance in natural ventilation in the different seasons of the year? The purpose of this study is introducing and analyzing the performance of Yazdi wind tower with numerical calculation Mechanic science to determine value and velocity of wind in it. Computer Modeling and Simulation methods and Logical reasoning method have applied in this article, and library resources studies was another part of research. Thus, first, each wind-tower has been modeled in computer environment, then after applying the climatic characterize, final simulation figures and diagrams have extracted in Vasari Autodesk 2.0 software. Simulated figures and diagrams extracted from the software in this paper as results indicate that increasing of the cooling power and optimized efficiency are one of the most important principles of wind-tower design process, and Yazdi wind-towers has mentioned this fact through 4 seasons of the year, and Kermani wind-tower, in opposite, mentioned this principle just in summers. . The height of wind tower did not affect directly on the analysis but also indirectly by making air turbulence and wind pressure was influential. By validate computer modeling and simulation, this paper clarify that our traditional ventilation systems has many undiscovered secrets and facts, which need further investigations. This article indicates that natural tactics, which has applied in the traditional architecture of Iran, could be mention as methods to using these valuable heritages in contemporary architecture.