NOVELTY - Producing organic fertilizer using marsh gas straws, involves (a) crushing straw, adding water to the crushed straw, wetting the straw, and adding nitrogen fertilizer, (b) piling the straw, and stacking straw, (c) adding straw to fermentation tank, and performing anaerobic fermentation, and (d) dehydrating and desulfurizing the obtained straw, and obtaining organic fertilizer.    USE - The method is useful for producing organic fertilizer and biogas e.g. methane.    ADVANTAGE - The method is cost-effective, produces no sewage, and improves utilization rate of renewable energy and comprehensive utilization rate of the straw resource.    DETAILED DESCRIPTION - Method of producing organic fertilizer using marsh gas straws, involves (a) crushing straw using straw crusher, where the length of the obtained straw is 15-20 mm, adding water to the crushed straw, wetting the straw uniformly for 24 hours, adding composite microbial inoculum into the straw, adding nitrogen fertilizer to the straw, and turning the straw, where the water content of the straw is 1.5-2 times more than that of the weight of straw, the straw comprises 60-70% of microbial inoculum, the adding amount the nitrogenous fertilizer is 0.15-0.25 wt.%, and the ratio of carbon to nitrogen in the fertilizer is 25:1, (b) piling the straw, stacking the straw, where the height of the piled straw is 1-1.2 m and thickness is 20-30 cm, covering the stack bottom with 10 cm space with proper ventilation, where the pile up time is 3-4 days, or 4-6 days and the temperature is 55-65 degrees C, and maintaining piles for 70-80 hours, where white hypha is produced on the surface of the straw, and the straw becomes soft and brown color, (c) adding straw to fermentation tank, adding nitrogen fertilizer (15-25%), uniformly mixing the material, where the total solid content of the material is 20-30%, and pH value is 6-8, sealing the fermentation tank, performing anaerobic fermentation for 30-40 days at normal temperature under solar energy as heat source, where heat insulating material, preferably polyurethane foaming material is provided in the fermentation tank, and the tank is made of steel plate, and (d) dehydrating and desulfurizing the obtained product, and obtaining organic fertilizer.