NOVELTY - Use of straw for preparing organic fertilizer, and preparation method of organic fertilizer are claimed. The method involves pre-processing straw, dividing pre-processed straw into dry and wet straw, drying wet straw, crushing dried straw, soaking dry straw in water, crushing wet straw, mixing crushed straws, auxiliary materials and leavening agent, adding water to mixture, stacking mixture, fermenting stacked material, drying fermented product, crushing dried compost, sieving crushed compost, packaging sieved fertilizer and storing packaged product.    USE - The straw is useful for preparation of organic fertilizer (claimed).    ADVANTAGE - The organic fertilizer has low cost. The preparation method is easy and convenient to perform.    DETAILED DESCRIPTION - Use of straw for preparation of organic fertilizer, and preparation method of organic fertilizer are claimed. The preparation method, involves (a) pre-processing straw, and dividing pre-processed straw separately into dry straw and wet straw based on moisture content inside straw, (b) drying wet straw or draining out water from wet straw having water content of more than 90% so that water content is maintained between 30-70% inside the straw, and crushing dried straw to obtain crushed straw having particle diameter of not greater than 2 cm, (c) soaking dry straw having water content of less than or equal to 10% and high hardness in water for 24 hours, and crushing wet straw to obtain crushed straw having particle diameter of not greater than 2 cm, (d) adding crushed straw, auxiliary materials and leavening agent to mixer, mixing components uniformly, adding suitable amount of water to obtained mixture, and maintaining water content of the mixture between 55-65%, (e) stacking mixture at fermentation site into heaps having bottom width of 1.8-3 m, top width of 0.8-1 m, high trapezoidal windrow of 1-1.5 m, and spacing of 0.5 m, (f) turning the heaps when temperature of heaps exceeds 70 degrees C, maintaining temperature of heaps below 70 degrees C for 48 hours after the start of the turning process, plunging stacked material at lower portion onto upper portion of the heaps during the turning process, and allowing complete fermentation to take place, (g) repeating the step (f) until heaps do not have any peculiar smell and stopping the fermentation process, (h) spreading fermented product evenly on drying space up to thickness of not greater than 20 cm, drying fermented product under sunlight, and tedding fermented product for allowing rapid drying of the fermented product when fermented product is not uniformly spread, (i) crushing dried compost having water content of less than 25%, and sieving crushed compost through sieve, and (j) packaging sieved organic fertilizer and storing packaged product.