Track quality (TQ) assessment of tactical data link is most crucial content in track processing, and is also the basis of tractical data link. in this paper, a new distance radius is presented to evaluate the track quality. at first, TQ area equation defined in the U.S. army tractical data link formatted message standard (TADIL) 6016 GB is introduced. meanwhile, according to the educing and analyzing this paper show that the track quality in U.S. army data link is defined by the elipse expression based on the x2 distributing, and the TQ area value equals to the area of elipse. moreover, a new distance measurement on TQ value is proposed, and the advantages also presented. finally, simulations show the affection of the geography location error, rader measurement error and extrapolation error on the TQ value.