The genomic DNA of H2-producing bacterium Ethanoligenens harbinense YUAN-3 was isolated and partially digested by Sau 3A I.The fragments of 2.5-5.0 kb were selected and inserted into BamH I digested plasmid pUC 19.The genomic clone library of strain YUAN-3 was constructed with 9 × 103 recombinants,indicating the coverage of clone library tends to be the theoretical value based on a 4.6 Mb average chromosome size of Clostridium,closest to Ethanoligenens harbinense.200 colonies were picked stochastically for sequencing and aligned with the database.The results imply that most of the sequences are similar with the hypothetical protein of hydrogen-producing bacterium whose complete genomes are sequenced,among which 49 sequences have the similarity over 70%,including folylpolyglutamate synthetase,DNA topoisomerase,acetyltransferase and so on,and 7 open reading frames (ORFs) of functional proteins or genes can be obtained.