The invention provides a high-temperature anaerobic cellulose decomposing bacteria strain (Thermoanaerobacterium sp.L-D, preservation registration No. CCTCC (China Center for Type Culture Collection) No: M208166, preservation date: October 17, 2008, preservation unit: CCMCC, and address: Wuhan University). The high-temperature anaerobic cellulose decomposing bacteria strain has strong decomposition capacity on filter paper and represents stronger decomposition capacity on straws. Meanwhile, the invention provides a culture medium for enriching and separate culture of the high-temperature anaerobic cellulose decomposing bacteria strain and a method for applying a product produced by degrading the straws by using the composite bacteria system, namely the high-temperature anaerobic cellulosedecomposing bacteria strain, to culture of SRB (Sulfate-reducing Bacteria).