Filling with unclassified tailings will expand the supply of filling materials with no need to build a dam for fine tailings. Theoretical and application study on unclassified tailing filling have been systematically carried out in U. S. , South Africa, Canada, Germany and China. The developmental process of this filling technology is presented and evaluated, including dynamic electrochemical consolidation, underground centrifugal dewatering and pumping, pipeline self-flow delivery and paste pumping of the highly concentrated unclassified tailings.