The invention provides a bactericidal sustained-release microsphere and a preparation method thereof. According to the method, a systemic triazole compound bactericide, i.e., difenoconazole-flusilazole technical, is used as a core material, and a degradable polymer material, i.e., polylactic acid, is used as a wall material; and a solvent evaporation process is employed for preparation of the bactericidal sustained-release microsphere. The preparation method of the invention solves the problems of easy drifting, easy degradation, low utilization rate and the like of traditional pesticides; andpolylactic acid is used as a wrapping material and has the characteristics of safety, low toxicity, easy degradation, environmental safety and the like compared with traditional chemical synthetic materials such as polyurea, urea formaldehyde resin, polyurethane and polyamide. Through compounding of pesticides and preparation of the sustained-release microsphere, a prevention and treatment spectrum is broadened; pesticide efficacy is improved; environmental pollution is reduced; prevention and treatment cost is lowered; and the requirements of pollution-free agricultural production are met.