Anaerobic ammonium oxidation (anammox), a microbial process where NH₄⁺ is oxidized to N₂ with NO₂^- as an electron acceptor is a critical part of the global nitrogen cycle, and anammox bacteria are responsible for up to 50% of the biogeochemical N₂ production in different ecosystems. Mangrove wetlands are periodically flooded by seawater, creating a high-salt and unstable-oxygen environment in the sediment where may survive more attractive and metabolism-specific anammox bacteria. However, little is known about the phylogenetic diversity, functional activity, and environmental adaptability of mangrove-derived anammox bacteria. In this study, vertical distribution and potential rates of anammox bacteria were investigated, and the co-occurrence of different genera of anammox bacteria was found in mangrove sediments, with Candidatus Scalindua and Candidatus Kuenenia being the dominant genera. Potential anammox rates ranged from 4.83 to 277.36 nmol N₂·g^-1·d^-1 at different depths of sediment cores, and the highest rates were found in the deeper layer of mangrove sediments. After enrichment, the abundance of Ca. Scalindua increased from 6% to 52.3% on day 420, and the stoichiometric ratio was close to the theoretical value of 1.146. Through metagenomics sequencing, 57 bacteria metagenome-assembled genomes (MAGs) were reconstructed, among them MAG EN2 represents a novel taxon within the genus Scalindua, for which the name Candidatus Scalindua mangrove sp. nov. was tentatively proposed. Sub-bioreactors were then set up, anammox bacteria affiliated with the genus Ca. Brocadia and Ca. Kuenenia (>65% for Ca. Brocadia and 35% for Ca. Kuenenia) with potential anammox rates of 46311 nmol N₂·g^-1·d^-1 were successfully enriched. Comparative genome analysis indicated that the mangrove-derived anammox bacteria have more specific gene-encoded proteins to adapt to high-salt and oxygen stress, such as peroxidases, sodium/potassium-transporting ATPase, accumulating amino acid glutamine, glycine, cysteine (inform glutathione), and proline metabolism to involve in cell osmotic regulation and protect intracellular nucleic acids, proteins, and lipids from ROS attack.