In order to carry out the appropriate program for agricultural operations and to know the appropriate planting time of dry wheat crops, the length of the growth period and its beginning and end are special. The studies carried out during the growing period of dry wheat in the country are based on the growth degree day method, which does not exist for dry or semi-arid regions. In this study, the length of the dry season wheat growth period for a statistical length of 30 years (1371 to 1400) for 38 sinopic stations of the country by taking meteorological temperatures and precipitation, with the help of the proposed method of the ecological zoning guidelines of the Food and Agriculture Organization of the United Nations (FAO) and By finding the intersection points of the graphs of precipitation and 50% potential evaporation and transpiration, the beginning and the end, the length of the growth period has been estimated, which corresponds to the results presented for the length of the growth period in the ecological classification publication of the FAO organization. Results of the obtained results, Astara station with 301 days of growth period and Isfahan, Saravan, Tabas, Semnan, Zahedan and Kerman stations with 0 days of growth period are respectively the most and the least. to give have given. Also, the results showed that the use of the FAO method to estimate the length of the growth period in arid regions obtains more realistic estimates than the growth degree day method.