The invention discloses a strain for directly producing butanol by utilizing xylan as a sole carbon source. A classification name of the strain is Thermoanaerobacterium thermosaccharolyticum, and the number of the strain is M5; moreover, the strain is preserved in China Center for Type Culture Collection (CCTCC), the preservation date of the strain is 27th February, 2017, and the preservation number is CCTCC NO: M 2017072. The strain M5 can basically degrade 30g / L of xylan in 3-5 days and can be used as the sole carbon source for growth; after the xylan is degraded into xylose, pyruvic acid is obtained by xylose isomerase and xylulokinase; subsequently, acetic acid, ethanol, butyric acid and butanol are obtained through a series of metabolic pathways. According to the strain and the application of the strain disclosed by the invention, enzymes of all pathways can bear a high temperature of 55 to 65 DEG C, and the strain M5 is the one that can produce the butanol by directly utilizing the xylan, which is the only reported bacterial strain until now; therefore, a series of high-temperature resistant enzymes can be provided for industrial production of the butanol, and the strain has important application value.