This paper seeks to answer the question whether the Constitutional Revolution of 1905-1911 in Iran was a democratic revolution or social revolution? This discussion has been explained from the view point of the political sociology, relying on the Moore's theory. Studies indicate that the Constitutional Revolution in all periods has had the features of democratic revolution for the following reasons: The revolution was led by bourgeoisie and land aristocracy in different periods. The revolution defended the legalism, established political freedom and applied the peaceful means more than other social revolutions.