TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The step of pre-treating the material involves processing the straws by hammer mill whose bottom screen is 3-10 meshes, treating the cracked straws by gas explosion through a continuous gas-explosion machine under vapor pressure of 2-3 MPa, where the pressure holding time lasts for 50-120 seconds, adding 0.1-0.3% of marsh compound bacterial agent and separated marsh liquor into the straws treated by gas explosion in the continuous gas-explosion machine until the moisture content of the material is 65-70%, and then mixing uniformly. The step of acidizing and fermenting the material involves (a) adding the uniformly mixed straws into an acidulating reactor until the volume of the uniformly mixed straws is 50-60% of the acidulating reactor, heating the acidulating reactor to 35-40 degrees C, adding compressed air for 5-10 minutes from the bottom of the acidulating reactor every 4-6 hours and aerobically fermenting the material for 2-3 days, (b) adding marsh liquor into the acidulating reactor until the volume of the marsh liquor is 90-95% of the acidulating reactor, maintaining the temperature at 35-40 degrees C and fermenting for 5-15 days in an anaerobic and acidic environment, adjusting the pH of the fermenting solution to below 6 by using diluted hydrochloric acid, (c) separating deposit by cyclone hydraulic separators, separating solid residue of the main components of fiber and lignin through 20-50 vibration filter sieve, filtering the residue liquid by a frame pressure filter, and then transferring the filtrate to marsh tank for fermentation. The step of fermenting marsh gas involves introducing the filtrate which contains 10-20% of organic matter into the marsh tank until the volume of the filtrate is 65-70% of the marsh tank, adjusting the pH to 6.5-7.5 by lime water, adding marsh suspending solution whose volume is 20-25% of the marsh tank, where the marsh suspending solution is used as inoculant, and where the total volume of the stuff is 90% of the marsh tank, maintaining the temperature to 35-40 degrees C, fermenting the mixture for 15-30 days in an anaerobic environment, collecting marsh gas, separating fermented marsh solution through a spiral separator to obtain 55-70% of marsh liquor which is used as fermenting solution, where 20-30% of marsh suspending solution is used as stain substrate for fermentation, and collecting 10-15% of mud which can be used as organic fertilizer. The method of extracting fiber and lignin involves, adding the separated solid residue into the reactor after the acidic fermentation process, adding 2-15% of sodium hydroxide solution, where the solid-to-liquid ratio is 20-30:70-80, stirring the mixture and heating to 80-100 degrees C, dissolving the mixture for 2-5 hours, filtering the mixture by centrifugation to obtain the filtrate whose main components are fiber and semi-fiber, bleaching and drying the filtrate to obtain the fiber product, adjusting the pH of the filter solution to 5-7 by diluted hydrochloric acid to precipitate and separate lignin, filtering lignin by centrifugation and then washing and drying to obtain the lignin product, treating the waste water by aerobic gas explosion until the quality reaches the discharging standard.