In plant cells, in addition to containing cellulose and semi cellulose, but also containing lignin (lignin). Lignin is a structure monomer with aromatic character, and it is a three dimensional deduction polymer composed of phenyl propane units. In the hardwood, softwood lignin content is 27%-32% (Gan Ji), the content of lignin grasses for 14%-25%. Although lignin is contained in all kinds of plants, the structure of lignin is very complex, and the structure of different plants is different, even in the same plant, the structure of lignin is different because of the different parts. Lignin is a non crystal, there is no melting point but a softening point, the lignin in the appropriate temperature (130-200) will soften, at this time to be a certain pressure to make the rest of the fiber and the other closely bonded with each other, cooling can be cured. Therefore, the use of heating extrusion method of crop straw fuel can be used without any additives and adhesives, greatly reducing the processing cost, but also meet the requirements of environmental protection. And the characteristics of the use of lignin heating softening, the appropriate increase in the temperature of the hot press molding is conducive to reducing the power of extrusion, biomass molding fuel is made of the principle of extrusion.