UWB ( Ultra Wide Band) technology is a new indoor positioning technology which has been widely studied for its low power consumption， high positioning accuracy and strong penetration ability. In this paper， based on the TDOA ( time difference of arrival) measurement method， UWB tags are used to send signals to multiple base stations to obtain the time stamp difference between tags and each base station， and the movement position of the tag is solved in real time by the Chan algorithm. The “current” statistical model is established， the iterative process of Kalman filtering is improved by setting the threshold， and them the improved adaptive Kalman filter algorithm is used to eliminate the influence of non line of sight error and noise on TDOA location so that the indoor positioning accuracy of TDOA is more accurate. Experiments show that the TDOA positioning method based on adaptive Kalman filter has high accuracy.