The present invention relates to a composite 
microbial agent, a preparation method thereof and an application in the preprocessing of kitchen garbage. The active ingredients of the composite 
microbial agent include 15 percent to 30 percent of bacillus stearothermophilus, 10 percent to 25 percent of 
bacillus licheniformis, 10 percent to 25 percent of 
zymomonas, 10 percent to 25 percent of 
agrobacterium, 15 percent to 30 percent of 
saccharomyces cerevisiae and 10 percent to 25 percent of candida, which are blended together. The composite 
microbial agent is prepared according to the following method: (1) the strains, which are preserved under the temperature of 4 DEG C, are respectively inoculated in ordinary broth media, the 
inoculation amount is 0.1 percent (v / v), and under the temperature between 28 DEG C and 37 DEG C, activating culture lasts for 8 to 18 hours; (2) the strains are then respectively transinoculated into ordinary broth media to be cultured for 8 to 18 hours under the temperature between 28 DEG C and 34 DEG C, the 
inoculation amount is between 0.1 percent (v / v) and 0.5 percent (v / v), and after culturing, microbial liquids are blended according to the proportion. The composite microbial agent can be used to preprocess kitchen garbage, inhibit the 
reproduction of pathogenic microorganisms in the kitchen garbage and reduce the deterioration and stink of the kitchen garbage, so that the kitchen garbage can be conveniently processed later, so the application prospect of the composite microbial agent is wide.