Vanadium (V(V)) contamination in groundwater poses a serious threat to human health. V(V) bioreduction is an effective method for vanadium contamination remediation. This study confirmed that ethane (C2H6) as an electron donor could realize efficient V(V) bioreduction. V(V) reduction by C2H6-based membrane biofilm reactor was enhanced with the increase of V(V) loading in the influent. Vanadium in the biofilm was mainly present as V(IV) precipitation. The C2H6-oxidizing bacteria Mycobacterium and Methylocystis used alkane 1-monooxygenase, alcohol dehydrogenase, and aldehyde dehydrogenase to generate metabolic intermediates, such as ethanol, acetaldehyde, and acetic acid, with the participation of O2, which were then utilized by V(V)-reducing bacteria Geothrix and Rudaea to reduce V(V) to V(IV) intracellularly and extracellularly under nicotinamide adenine dinucleotide (NADH) and cytochrome-c oxidase. This result could promote the application of C2H6 in the ex-situ remediation of V(V)-contamination groundwater.