The hot, dry and exhausting climate of the natural environment of Sistan region has caused the people of Sistan to invent valuable experiences in adapting to the environment in different historical periods. Therefore, it is necessary to identify historical experiences such as the valves built in Macchi Castle as one of the ancient artifacts of the Safavid period in compatibility with the environment and make efforts to use this knowledge. Therefore, the aim of the research is to investigate the natural ventilation in the open living spaces of Macchi Castle in Sistan using the CFD method with an emphasis on the northern porch porthole. The question of the present research is raised as follows: How has the northern porch porthole of Macchi Castle functioned in terms of structural compliance with the direction of the 120-day winds of Sistan? The research method is descriptive-analytical and based on library and field studies in the ancient city of Howzdar Sistan and Macchi Castle, and computational fluid dynamics (CFD) analytical software is used for wind simulation. Due to the complexity of the architecture, the geometric volume (mass) of Macchi Castle was produced in Ansys Fluent and 3D Max software. Grid independence was implemented with Ansys Meshing software. Meteorological data and WRPLOT View software were used to identify wind parameters. The CFD simulation results show that the "wind speed" in the northern porch section covers the numerical range between m/s 0.4505285 and m/s 0.5300041. Also, the "direction of the wind" moves towards the south wall as soon as it enters the straight gate and slightly inclined to the right and enters the central courtyard through the porch. CFD outputs and archeological data confirm the performance and use of 120-day Sistan winds in the warm months of the year in the northern porch of Macchi Castle