The central yard, as an efficient and responsive device, has done its job well in protecting residents from environmental, social and cultural conditions in different regions of Iran. The physical typology of the central courtyard in different regions of the country, especially the buildings related to the first Pahlavi period, is a topic that this research seeks to answer. For this purpose, traditional houses with courtyards from different cities of the country have been selected as study samples. This research aims to investigate the physical structure, patterns and various types of the central courtyard in traditional houses, to study the typology of these houses. In order to carry out the research, more than 60 examples of traditional houses in the historical area of different cities of Iran were identified and 23 houses that had complete information and documents were selected for classification. According to their nature, research data has been collected by referring to library sources and field observations. The results of the classification of the location of the courtyard in the building show that one construction front (with the building mass on the northern side of the courtyard) has the most and buildings with two courtyards on both sides of the building have the lowest frequency among the samples studied. Also in In the longitudinal classification, 15.1-25 has the highest frequency, while in the transverse classification, the maximum frequency belongs to 15.1-20. Yards with an area of 100 to 400 square meters have the highest frequency among the samples studied. In the classification of proportions, the highest frequency is related to the proportions of 1.1 and the lowest is related to 1.5, which indicates the stretching of the yards towards the square. After the classification and comparison, Tousizadeh house has been chosen as the representative of the species with the highest abundance and Ganjalizadeh house as the representative of the species with the least abundance in the study context.