A quick-fermentation decomposing agent for livestock and poultry manure treatment and a preparation method thereof. The weight composition of the rapid-fermentation decomposing agent per 100g is: β-D-glucose 10.0-50.0g, glucose oxidase 0.01-3.0g, Catalase 0.01~1.0g, polyethylene glycol 1000 1.0~10.0g, polyethylene glycol 2000 1.0~5.0g, polyethylene glycol 8000 1.0~30.0g, mannan oligosaccharide 0.1~5.0g, xylan 0.1 ~5.0g, the balance is cornstarch. The invention further discloses its preparation method, which has strong process operability, low input cost, is beneficial to production transformation, and has good market prospect. The fermentation decomposing agent of the invention has the effect of quickly killing pathogens in livestock and poultry manure, can significantly shorten the time required for the composting fermentation process, enables the manure to be used as a resource for secondary use, reduces breeding pollution, and is beneficial to environmental protection.