Historically, Bandar Lengeh has been the main seaport of Larestanand the transaction hub of the import and export of goods in the Persian Gulf since 1834. The port maintained its authoritative position until 1897, but from then onward, the social and business dynamism of Bandar Lengehdevolved. Studies done on the issue emphasize on the economic factors in the social devolution of Bandar Lengeh but it seems that factors affecting the social devolution of Bandar Lengeh were not merely economic, but rather equally political and ideological in turn. The current descriptive-analytic study analyses the two other factors, i. e., political and ideological structure of Bandar Lengeh, besides its economic structure, via application of Louis Althusser’ s over-determination theory. The tested hypothesis is: “ Structural contradictions (political, economic, and social contradictions) led to the social devolution of Bandar Lengeh” . In fact, since 1899, political, economic, and social contradictions had invaded Bandar Lengeh. New customs duties or tariffs of 1899, imprudence ofnone-native and governmental officials of customs, social and political insecurity in the coasts of Lengeh after the Constitutional Revolution, the monopoly law for government business, the compulsory military service law, the command of “ mandatory unveiling” , and the ways of escape from these contradictions (human and capital migration, smuggling, and bribery) all led to the social devolution of Bandar Lengeh.