Abstract: Anaerobic hydrocarbon degradation in oil reservoirs has gained considerable attention owing to its extreme environment and significant affect on oil recovery. Despite the fact that anaerobic hydrocarbon degradation has been extensively studied under various environments, the in-situ degradation mechanism in oil reservoirs remains poorly known. With the development of sequencing technology, omic-based analysis will be increasingly applied in oil reservoir samples, providing a new methodology for revealing the hydrocarbon degradation process in this specific geological environment. This review summarized recent advances in in-situ hydrocarbon degradation researches in oil reservoirs and metagenome-based analysis of oil reservoir samples, providing new insights for further~studies.