Distribution network automation system is the key to realize self-healing control of active power distribution network, and intelligent terminal (DTU) is the core equipment. In the centralized distribution network automation system, FTU has only monitor and control function, the main station and the terminal are too dependent on the communication network, once the communication network is in trouble, it is difficult to realize the distribution network fault isolation and restoration of power supply. In this paper, design a distribution intelligent terminal which is suitable for active distribution network system based on intelligent distributed distribution network automation technology, it is based on the original FTU monitoring and control functions, adding line protection function, in place to achieve the fault isolation and restoration of power supply. According to the characteristics of active distribution network this paper put forward the improvement scheme and adaptive differential protection setting strategy, the terminal working method has been verified by the Matlab/Simulink simulation model and it has important guiding significance to the study of intelligent distributed automation system.