Abstract: It is very hard to develop encryption technology used in cheap RFID（Radio Frequency Identification） tags.In this paper，intrusion detection，as a new methodology，is adopted to create security model for RFID system.By analyzing typically security attacks on RFID systems，a solution to get characters of intrusion by integration and statistics of channel log and application log is proposed.A multi-agent structure of RFID intrusion detection is designed based on biological immune mechanism.A BDI model of detector produce agent is designed based on immune tolerance.A BDI model of detecting agent is designed based on multilevel defense and immune memory.At last，multilevel，adaptability and robustness of the model are analyzed.