A bactericidal disinfectant solution for Miscanthus and its preparation method. The disinfectant solution is made of the following raw materials in parts by weight: 1-2 parts of gallic acid, 0.1-0.2 parts of L-1,2-dehydro-α-cyperene, and 0.1-0.2 parts of calamus 0.1-0.2 parts of alkenediol, 0.4-0.6 parts of hyoscyamine, 0.4-0.6 parts of phosphatidic acid ethanolamine, 1-2 parts of Bletilla striata dihydrophenanthrenopyranol, 0.5-1.2 parts of methyl corydalis, 10 parts of violet water -15 parts, 0.2-0.5 parts of eucalyptol, 14-20 parts of modified plant extract, 260-300 parts of deionized water. The disinfectant of the present invention has the function of sterilization and disinfection, can kill 100% of the bacteria in pampas grass, and the disinfectant has a certain self-cleaning ability, the disinfectant after use can be reused after standing, and the disinfectant can be used repeatedly for 5-6 Second, the utilization rate is high, the viscosity of the disinfectant is low, it is not easy to stick to Miscanthus, and it can improve the anti-corrosion and flame-retardant properties of Miscanthus, greatly improving the service life of Miscanthus brooms.