  We demonstrate that the dynamics of quantum coherence serves as an effective
probe for identifying dephasing, which is a distinctive signature of many-body
localization (MBL). Quantum coherence can be utilized to measure both the local
coherence of specific subsystems and the total coherence of the whole system in
a consistent manner. Our results reveal that the local coherence of small
subsystems decays over time following a power law in the MBL phase, while it
reaches a stable value within the same time window in the Anderson localized
(AL) phase. In contrast, the total coherence of the whole system exhibits
logarithmic growth during the MBL phase and reaches a stable value in the AL
phase. Notably, this dynamic characteristic of quantum coherence remains robust
even with weak interactions and displays unbounded behavior in infinite
systems. Our results provide insights into understanding many-body dephasing
phenomena in MBL systems and propose a novel feasible method for identifying
and characterizing MBL phases in experiments.
