The phase delay software is a key component of VLBI (Very Long Baseline Interferometry) orbit determination system in CE-4 mission, which is critical to deep space exploration. When processing X-band DOR (Differential One-way Ranging) signals of probes in the past, group delay jumping occasionally occurred in the observed scan. This paper consists of two parts. First, according to the VLBI station signal reception and VLBI center data processing steps, we analyzed the frequency, phase, power and self-correlation spectrum of the signal and located the influencing factor at the abnormal analog signal of Kunming (KM) station. Second, the group delay jumping was revised by the post-correction method which was based on the analysis of the abnormal unwrap phase. We used the corrected phase to get the new group delay and used orbit determination software to verify the effectiveness of the post-correction method which upgraded the phase delay processing software.