Abstract: Emergy analysis is one of the most effective means to study overall efficiency of the agro-ecosystems.This article briefly introduces the beginning and development of the theory and methods of the science.A comparison with the traditional energy analysis,ecological footprint,life cycle assessment,etc.is presented.Recent advances on its application for overall efficiency of agro-ecosystems are summarized.And,some existing problems and possible future direction of research in the field are also discussed.