The invention relates to a method for controlling phytophthora parasitica, belongs to the field of flue-cured tobacco planting and provides a sustained-release agent method for controlling phytophthora parasitica. The method comprises specific steps as follows: corncob carbon is adopted to adsorb a drug for controlling phytophthora parasitica and then is buried at the root and tuber parts of flue-cured tobacco. The corncob carbon is adopted and is loose and porous, so that more agent or more fertilizer can be adsorbed, the sustained-release function can be realized when the corncob carbon is placed at the root part of the plant, the speed of the agent or the fertilizer leached by rainwater can be decreased when the corncob carbon is washed by rainwater, the agent is kept to act on the root and tuber parts of the plant, the use quantity of the agent or the fertilizer can be saved, and the number of fertilizer or agent application times is reduced. With the adoption of the method, phytophthora parasitica can be effectively controlled, the method is also suitable for controlling black shank of other crops as well as a few soil-borne diseases and insect pests, and the use quantity of pesticides and workload are reduced.