The invention discloses a microbial agent for preventing tobacco wildfire and brown spot, and a preparation method of the microbial agent, and belongs to the technical field of environment-friendly prevention and control. The microbial agent is prepared from the following components in percentage by volume: 12-25% of achromobacter sp., 6-13% of enterobacter sp., 5-15% of ochrobactrum anthropl, 46-58% of stenotrophomonas sp., and 8-12% of bacillus subtilis. The preparation method of the microbial agent comprises the steps that the compound microbial agent is prepared from bacteria solutions ofthe achromobacter sp., the enterobacter sp., the ochrobactrum anthropl, the stenotrophomonas sp. and the bacillus subtilis according to the volume ratio, and the compound microbial agent is applied ina mist spraying mode and is applied to the front faces and the reverse faces of leaves. Experiments show that the prepared microbial agent has the quite high inhibiting effect on tobacco brown spot and wildfire pathogenic bacteria, shows the great disease prevention effect on the tobacco brown spot and the tobacco wildfire, is low in cost, good in effect and environmentally friendly, and thus hasthe great biopesticide development prospects.