Abstract: For location precision of LANDMARC affected by underground non-line-of-sight error, multipath effect and tag collision, LANDMARC location algorithm was improved from the view of measurement of received signal strength indication value, selection of received signal and tag anti-collision. The improved LANDMARC location algorithm judges the nearest reference tag by measuring the received signal strength indication value directly, abandons error signal through Gaussian filter, sets reasonable timeslot for signal sending according to tag number and resets the timeslot at tag collision time. The simulation results verify effectiveness of the improved LANDMARC location algorithm.