To improve the precision of distance measure, Kalman and α-β algorithm are used in distance filter. To guarantee processing precision, many variables are used in Kalman algorithm. The α-β algorithm is a kind of constant plus filters. The volatilizable phenomena would happen. Considering the shortage of Kalman and α-β , a kind of real-time distance track algorithm for TACAN based on variable dimension Kalman filter is proposed. Non-maneuvering model and maneuvering model of distance measuring are constituted. The adaptive filter may be converted between non-maneuvering models and maneuvering model, and the real time distance track for TACAN is accomplished. The result of Monte Carlo simulation indicates the algorithm can achieve the real time distance track and the precision is improved obviously.