The dynamic reconstruction system and method of intelligent electronic devices（IEDs）for substations are studied.IED can support plug and play and state monitoring by introducing the universal plug and play（UPnP）protocol and taking advantage of IEC 61850.The design method of universal IED is also given.The failure of IED can be detected quickly by evaluating the operational status of IED using the Petri net fault diagnosis method.With the options of mirror mode and general mode，the main automation functions of the fault IED can be dynamically reconfigured in the standby IED in a safe procedure.After building the universal IED prototype and the supervision host，such functions have been tested on plug and play，state supervision，state assessment and dynamic reconfiguration.The results show that the UPnP protocol can effectively achieve IED discovery，monitoring，administration and control while fully meeting the requirements of plug and play.The monitored state variables can intuitively reflect the operational status of IED.The dynamic reconfiguration method has important application value in providing substation automation system with alternative maintenance options and higher availabilities.