The independence referendum of Catalonya, the autonomous community in Spain, brought about a confrontation between Spain's central government and the local autonomous government and drew international attention. What is the historical factor for the Catalan independence referendum? And what is the difference between propositions of law from the two parties? This article reviews the development of the Catalan independence referendum from legal and social factors from the whole story of referendum, the resentment between Catalonia and Spain, the ongoing conflicts between local and central government regarding the European debt crisis in 2009, to the argument of the development of Spain's referendum law and constitution.