Abstract: Very long baseline interferometry (VLBI) can provide accurate plane of sky measurement of spacecraft. Based on the first implementation of interferometric tracking in CE'3 project by China DSN (Deep Space Network), this paper describes modeling interferometric tracking with TT&C mode. Earth based stations keeps pointing to the spacecraft while it is in view of antenna. So interruption of TT&C signal can be eliminated, which is unavoidable with traditional short-scan working mode. Compared with high accuracy orbit ephemeris, delay observable error is less than 1ns which corresponds to an angular accuracy of about 97nrad (37m uncertainty at the Earth-Moon distance). Accuracy of delay observable is in the same order with CVN baseline which has the similar configuration.