The active distribution network（ADN） is an effective approach to solve the problems such as the high-penetration of intermittent renewable energy， interaction between grid and charge-discharge facilities， and also the analysis and operation of smart grid. This paper focuses on the definition of ADN and its characteristics. Based on the analysis of current research status， some ADN key technologies are proposed， including the unified planning for ADN， the coordination control based on both distributed autonomy and global optimization， the advanced distribution management system with flexible approach for power flow management， and also multiple objectives for economic evaluation.