The invention discloses a medium for improving the antibacterial activity of biocontrol bacillus to plant pathogenic fungi, comprising the following components: potato, sucrose, maize paste, sodium L-glutamate, phosphate, MgSO4.7H2O, CaCl2, ferric citrate, MnSO4.H2O, phytic acid, L-proline, threonine, tetramethyl glutaric aciduria, gamma-aminobutyric acid, sodium nitroprusside, hydrocortisone, LaCl3, amino-oligosaccharin, chamomile leach liquor, and celery juice. A biocontrol bacillus seed solution is inoculated into the medium for temperature-variable fermentation culture, so as to promote the growth and reproduction of bacillus, and effectively stimulate the activity of bacillus, enhance the secretion of bacteriostatic substances and the activity of pathogen hydrolase, thereby significantly improving the antibacterial activity of bacillus to plant pathogenic fungi such as fusarium oxysporum, verticillium dahlia, botrytis cinerea, sclerotinia sclerotiorum, and providing a theoreticalbasis for the further development and application of biocontrol bacillus.