Abstract: The synthesis,structure elucidation and fungicidal activity of a new compound,the complex of diacetonamine oxalate-copper(Ⅱ),were reported.The target compound was prepared by diacetonamine oxalate and copper chloride in deionized water,and its single crystal was obtained in alcohol.The chemical structure was analyzed by elemental analysis,IR and X-ray single crystal diffraction analyses.Its toxicity of inhibiting spore germination against six species plant pathogen were also tested.The results showed that the molar ratio(2∶ 1∶ 2) of oxalic acid,copper,and diacetonamine in the complex exhibited remarkable fungicidal activity against tested agricultural pathogen,its toxicity approximated to zineb 800 WP.