Anammox bacteria can perform anaerobic ammonium oxidation,a long missing process which contributes 30%~50% to dinitrogen gas in marine nitrogen cycling.The potential role of anam-mox bacteria coupling with ammonium oxidizing bacteria and archaea will benefit to elaborate the complex mechanism of marine nitrogen cycling.Furthermore,the unique cell and genomic characteris-tics make anammox bacteria an important model microorganism to explore the bacterial evolution.Here we reviewed the current status of molecular ecology of marine anammox bacteria and give a perspective into the future based on our understanding of the literature and our own work.