The lunar rendezvous and docking technology is an important guarantee for our third phase of lunar exploration. In this paper, by using the VLBI (Very Long Baseline Interferometry) delay of CE03 (Changé-03) which was around the moon, the changing of differential group delay (DGD) under the SBI (same-beam VLBI) observation mode was simulated. The simulation results indicated that the orbit distance between orbiter and ascender was kept in 100 kilometers and it lasted for half an hour. The track information of these two were well reflected by DGD which can be used for orbit determination. In the approach stage, DGD is rapidly approaching to 0, as the ascender accelerated and closed to the orbiter, while the orbit distance was reduced from 5km to 20m, and was rapidly increased as the ascender was far away from orbiter. At last, using the VLBI delay of CE03 which was halfway to the moon and transmitted two DOR (Differential One-Ranging) signals that were observed by CVN (Chinese VLBI Network), we calculated DPD (Differential Phase Delay) and preliminarily showed the error of DPD.