Abstract: In part one of this series paper,the big data thinking and the macro energy thinking have been explained.On one hand,the energy system is considered in the context of the cyber-physical system,to break down the physical barriers among power system,primary energy system and end-use energy system.On the other hand,the private network and the Internet are combined together to constitute the communication system,to break down the barriers between operation and business activities.Thus,the above-mentioned physical and information systems can be integrated into a cyber-physical system,through causal data,statistical data,gambling data and corresponding big data technology.Along this direction,this paper explores the applications of power（energy）big data.Based on several topics that have been studied,the significance and approaches of big data technology in enhancing the economy and reliability of energy flow in different spatial and temporal scales are induced,which include:1 introduce casual analysis measures to topics that usually relied entirely on statistical analysis,to improve the applicability and accuracy;2 introduce statistical analysis measures to topics that usually relied entirely on casual analysis,to enhance the efficiency; 3 combine casual analysis,statistical analysis and experimental economics simulation analysis,to create a new research area of what a single analysis paradigm cannot solved,such as the interactions between the macro energy system and the natural environment,the social environment,market economy,policy and other non-energy sectors.