Changing religion in Iran has always been important issues to the attention of researchers, Because this type of change itself creates major changes in social, cultural and even political structures and institution. Tendency to Shiite in Iran always causes arguments and disagreements between researchers and different views were expressed on this issue. This study seeks to address the role of the advocacy Organization(sazman e vekalat) in the change of religion in Iran. Also this study tries to show social order in Sassanid, besides representing the mechanism of religion change in Iran and utilization of
advocacy Organization from this situation. Therefore, by the use of signs that indicate the activity of advocacy organization in different regions of Iran, will show that the advocacy organization by cultural confrontation and with focus on villages leaded to the spread of Shiite in Iran.