NOVELTY - Producing methane and organic fertilizer involves crushing giant king-grass; performing wet fermentation by using normal fermentation gas, a high temperature wet fermentation for 5-8 days in 5-15% fermentation liquid at 50-60 degrees C, or high temperature and humidity to ferment for 10-15 days in 5-12% fermentation liquid at 30-40 degrees C; separating biogas slurry and biogas residue, adding degraded biomass with microbial agent to separated residue, mixing uniformly and spraying on surface splashed with clarified lime water for 5-10 days; and performing high temperature dry yeast fermentation.    USE - For producing methane and organic fertilizer (claimed).    ADVANTAGE - The method produces methane in high yield of 596.26 m3/tTS; utilizes biogas which is clean renewable energy, thus reduces the use of fossil fuel; avoids waste discharge and environment pollution; and is cost effective and eco-friendly. During dry fermentation stage the present method utilizes dry yeast, thus saves water and energy. The obtained organic fertilizer improves quality of soil, and prevents side-effects caused by applying fertilizer to soil.    DETAILED DESCRIPTION - Producing methane and organic fertilizer by using wet and dry fermentation of giant king-grass, involves: crushing giant king-grass as raw materials; performing wet fermentation by using biogas slurry of normal fermentation gas, a high temperature wet fermentation for 5-8 days in 5-15% the fermentation liquid at 50-60 degrees C, or high temperature and humidity to ferment for 10-15 days in 5-12% the fermentation liquid at 30-40 degrees C; separating biogas slurry and biogas residue, where biogas is used as inoculum of the next fermentation, adding degraded biomass with microbial agent to the separated biogas residue, mixing them uniformly, and spraying on the surface splashed with clarified lime water for 5-10 days; performing high temperature dry yeast fermentation for 10-15 days in 18-25% fermentation material liquid at 50-60 degrees C, and performing dry yeast fermentation for 15-25 days in 18-28% the fermentation material solution at 30-40 degrees C; and producing organic fertilizer. The short wet fermentation adopts completely the biogas slurry, without adding water or in order to ensure the material liquid total volume only adding a small amount of water; uses batch fermentation, that is after the first time, a no longer, until after a short wet fermentation residue-liquid separator, for a short time of wet yeast; and is performed at high temperature and humidity to ferment for 5-8 days at 53-57 degrees C, and a temperature and humidity to ferment for 10-15 days at 33-37 degrees C. The dry fermentation is carried out by using biogas residue and normal dry yeast as the inoculum at a concentration of 1/5 to 1/3, and processing obtained residue, uniformly mixing the dry yeast with water, followed by adding into anaerobic dry fermentation tank, removing oxygen in the fermentation tank by marsh gas or nitrogen, and sealing constant-temperature fermentation. The dry fermentation step is carried out without adding nitrogenous fertilizer according to a carbon nitrogen ratio is more than 30, and adjusting livestock and poultry manure to less than 30. The high temperature dry yeast fermentation is carried out for 10-15 days at 53-57 degrees C, and dry yeast fermentation is carried out for 15-25 days at 33-37 degrees C. An INDEPENDENT CLAIM is included for the production of organic fertilizer involving: mixing the obtained dry fermentation biogas residue further dried to a water content of less than 20 wt.% of the dry biogas residue so as to crushing to the particle size, adding auxiliary material and uniformly mixing, granulating, shaping, sieving and packing.