NOVELTY - Crop straw is processed to length of 3-5 cm, and water is added to wet straw filament. The resultant straw is fermented and filtered. A sodium hydroxide solution is added to resultant solid to adjust alkali content, stirred, and supernatant containing hemicellulose is concentrated, to obtain hemicellulose. The sodium hydroxide solution is added to the resultant solid to adjust alkali content, stirred, resultant slurry is processed, and filtered, to obtain feed additive. The filter press liquid is concentrated, acid is added to adjust pH to 3-5, and filtered, to obtain humate.    USE - Preparation of hemicellulose, humate and feed additive (claimed).    ADVANTAGE - The method enables economical preparation of hemicellulose, humate and feed additive with reduced process chemical, by simple method.    DETAILED DESCRIPTION - Crop straw is processed to length of 3-5 cm in kneading machine, and water is added to wet straw filament. The ratio of straw filament and water is 1:5-1:10. The resultant straw is fermented using 0.1-5% fermentation agent at humidity of 70-95% for 0.5-10 days, resultant straw is filtered using filter press and fermentation liquid is collected. A sodium hydroxide solution or potassium hydroxide solution is added to resultant solid to adjust alkali content of the solid to 4-10%, agitated at 50-80 degrees C for 1-8 hours, resultant mixture is aged, solid and liquid are separated from the resultant mixture, and supernatant containing hemicellulose is concentrated to 1/10 of the original volume, to obtain hemicellulose. The sodium hydroxide solution or potassium hydroxide solution is added to the resultant solid to adjust alkali content of the solid to 5-30%, stirred, resultant slurry is processed at 100-120 degrees C for 60-130 minutes, filtered using filter press to obtain feed additive, and filter press liquid is collected. The filter press liquid is concentrated, acid is added to adjust pH to 3-5, and filtered, to obtain humate. The resultant filter liquid is concentrated, dried and used as raw material for producing organic fertilizer.