Objective：To characterize the biological properties of a pathogenic bacteria separated from blood sample from a patient with endocarditis，and then to investigate the pathogenesis preliminarily. Methods：Isolates were initially identified by standard bio－chemical tests including micro biochemical tubes. The bacterial 16 S ribosomal RNA gene（16 S rRNA） was sequenced for molecular biological identification. Biofilms of the isolates were formed in vitro by standard methods. Results：The phenotypic and genotypic re－sults of the isolate were corresponded well with those of Neisseria elongata spp. nitroreducens. In vitro model exhibited the ability of isolates to develop mature biofilms. Conclusion：The reported first case of endocarditis due to Neisseria elongata subsp. nitroreducens in China may attract the attention of clinical microbiologist in identifying this organism.