Anaerobic digestion, which could transform organic wastes to biological natural gas, emerged from the discovery of biogas. It is drawing mounting attention due to its pollution treatment and energy recovery. The realization and advancement of anaerobic digestion depends on the development of technology and basic theory. Therefore, this paper will describe current mainstream anaerobic digestion technologies through configurations and theories. Firstly, we summarize the current mainstream anaerobic digestion technologies, introduce their design and configuration, and discuss the internal improvement and transformation. The sludge-water separation distinguishes the first and second anaerobic digestion technologies while granular sludge develops the third anaerobic digestion technology. Secondly, we describe the anaerobic digestion theory, and explain its role in anaerobic digestion revolution and also provide some improvement strategies. The design and operation of anaerobic digestion technology are greatly improved by the understanding of anaerobic digestion theory and discovery of interspecific electron transfer. Then, we introduce some emerging technologies and theories which will strongly promote anaerobic digestion. Machine learning will help unravel the complex black box of anaerobic digestion while synthetic biology will redefine anaerobic digestion. Finally, we discuss the future anaerobic digestion technology. The anaerobic digestion will be more efficient, intelligent and customized. In the future, it will become a green platform to complete the social cycle of energy and substance.