The invention discloses a hydroxyquinoline compound as well as a preparation method and application thereof in preventing and treating agricultural diseases. Testing results show that the compound hasremarkable activity upon corn leaf fulvia fulvum, cotton oxysporum, potato rhizoctonia solani kuhn, didymella bryoniae, fusarium oxysporum, wheat gibberella, rice blast, botrytis cinerea, lycium barbarum anthracnose, cotton anthracnose, sclerotinia sclerotiorum, pepper phytophthora blight, potato late blight, rhizoctonia solani, melon bacterial fruit plaque bacteria, grape meloidogynosis bacteria, Chinese cabbage erwinia carotovora, kiwi fruit anabrosis bacteria, pseudomonas lachrymans, ralstorinia solanacearum, rice bacterial leaf blight and rice bacterial stripe bacteria. The hydroxyquinoline compound is simple in preparation process, cheap and easy in raw material obtaining, high in product purity, good in bioactivity and wide in sterilization spectrum and has the potential of being developed as new fungicides.