Abstract: This paper was based on the application background of wireless intrusion detection system,which wants to locate target host,but can not predict transmitted power of target’s wireless network card．By using received signal strength indication difference for the least square calculation,which is based on the transformation of Shadowing model,the method can eliminate the dependence of transmitted power parameter．By means of the design,realization and test of the positioning module for wireless intrusion detection system,the feasibility of the method was verified．Finally,an indoor three-dimensional positioning module with Room-level precision was achieved in WIDS．Experiment data shows that precision and cost of the system are integrally optimal as a space point can be covered by 8detection nodes.

Key words: Three-dimensional positioning,Wireless intrusion detection system,RSSI,Shadowing model,Least square