Multi-functional biological agent containing bacillus subtilis

The invention provides bacillus subtilis DLD2 bacterial strain which is preserved in a China general microbiological culture collection center (CGMCC), the serial number is CGMCC NO.3222. The invention further provides a multi-functional biological agent formula and a preparation method thereof; fermentation broth, fulvic acid, zinc sulfate and other components of the bacillus subtilis DLD2 are formulated for preparing the multi-functional biological agent formula which is used for improving soil and continuous cropping resistance; the biological agent has the following functional effect: (1) bio-control microorganisms are utilized to prevent harmful flora from infecting plant and killing pathogenic bacteria, induce the plant to generate disease resistance and prevent seedling withering and rotting; (2) by utilizing synergia effect of formulation of the bacillus subtilis, fulvic acid and zinc sulfate, the root system growth can be induced, plant regeneration and root regeneration are realized, soil hardening is broken, granular structure is formed, no deep tillage is realized, moisture holding and soil moisture conservation is realized, fertilizer damage is relieved and soil fertility is improved.