Dehdasht is one of the most important cities of southwestern Iran during the Islamic era, which was of great importance and prosperity in the Safavid period. This city was in the Safavid era the  Dar al -Molk and the ruler of the large province of Kohgiluyeh, which covered the Arrajan wide area. The city of Dehdasht, during its period of prosperity, had all the signs of an urban center. The purpose of this paper is to analyze and examine the factors contributing to the decline of the city of Dehdasht from the Safavid period to the end of the Qajar era and the time of its decline. In this study, which has been conducted using a historical-analytical method, an attempt is made to answer the question of what factors led to the decline of the historic city of Dehdasht, and to which period in history does the end of its political and social life belong? Based on the results of the analysis of historical sources and archaeological studies, war and riots and successive looting, insecurity, destruction of communication networks, decreased business prosperity, heavy taxation and deterioration of the economic situation led to the decline of the historic city of Dehdasht and the city's emptying of the people. The weakness and gradual decline of the city also began with the weakening of the Safavid government and continued until the Qajar period, but the final collapse and end of its political and social life dates back to the late Qajar period.