Base on the application characteristics of BitCloud protocol stack, ATmega128RF microcontroller RF characteristics, ZigBee network structure, filtering algorithms, and position estimation methods, described in detail the main content of indoor positioning systems and the implementation of key technologies. In the position estimation methods proposed smoothing filter, combined with maximum likelihood estimation method to an effective way to estimate the position. Experimental results show that the algorithm is more stable than ordinary RSSI algorithms, and high positioning accuracy.