The invention provides a microbial bacterial agent, a preparation method thereof and a method for treating animal excrements by using the microbial bacterial agent. The microbial bacterial agent can quickly decompose organic matters in the animal excrements, effectively remove odors of the animal excrements and reduce the content of harmful substances in the excrements. In addition, in the treatment method of the animal excrements, because the cultivation of animals is carried out on a base stock inoculated with the microbial bacterial agent, after the animal excrements are discharged, the harmful substances in the excrements can be directly discomposed by the fermentation of microorganisms in the base stock; thus, the animal excrements and the used base stock can be used as raw materials for producing organic fertilizers, the transformation from waste into the organic fertilizers, and the like of the animal excrements is finished, and the problem of environmental pollution caused by excrements generated by scale animal cultivation is thoroughly solved.