The invention discloses a drug sustained-release alginic acid embolism microsphere and a one-step electrostatic spraying preparation method thereof. Sodium alginate is compounded with a chemotherapeutic drug with positive charges, and the drug-loaded alginic acid embolic microsphere is prepared through a multi-nozzle one-step electrostatic spraying technology, so that combined treatment of embolism treatment and chemotherapy is realized. According to the multi-nozzle one-step electrostatic spraying preparation method provided by the invention, the drug sustained-release embolism microsphere can be prepared in one step, the prepared microsphere is uniform in particle size and controllable in size, the diameter is 100-1000 microns, and the microsphere has the potential of large-scale production. According to the alginic acid embolism microsphere provided by the invention, the drug loading capacity of common embolism microspheres is greatly improved, long-term slow release of chemotherapeutic drugs can be realized, nutrient source blood supply required by tumor growth can be blocked, the local drug concentration of a focus part can be improved, and meanwhile, the drug concentration inother organs is reduced, toxic and side effects are reduced, synergistic treatment of embolism treatment and chemotherapy is achieved, and the method has great development prospects.