The invention belongs to the field of medical fertilizers, and in particular relates to a plant medical fertilizer for preventing and treating fly injurious insects. The plant medical fertilizer for preventing and treating fly injurious insects comprises a component A and a component B, wherein the component A is a preventive agent which comprises tea bran powder and tobacco powder; and the component B is a fertilizer which comprises plant ash and a calcium magnesium phosphate fertilizer. The plant medical fertilizer provided by the invention is hugely remarkable in preventing and treating effect, does not pollute the environment and harm human health, and can be used as a crop weight-gaining and fruit and vegetable acidic soil improver.