Agent-based wide-area backup protection（WABP） which can improve the security of power system has been studied in recent years. The information model of wide-area backup protection agent based on IEC 61850 is proposed. According to a kind of WABP algorithm， a general architecture of WABP multi-agent system， which is decentralized， distributed and equal negotiation， is given. Besides WABP agent， the components of logical nodes in protection IED are expatiated， as well as the collaboration relation and multi-task based information flow among them. The WABP agent is designed to an extended logical node， which includes interface layer， advanced process layer and basic method layer. The remote message transferring principle for WABP agents locating in different substations is studied. The communication is accomplished with two-phase submission. According to different types of messages， UDP or TCP is chosen to transmit them. The information model of WABP agent has been designed in EPOCHS platform and validated to be effective.