The invention relates to a supercapacitor electrode composite material and a preparation method thereof, belonging to the technical field of energy storage and conversion. The electrode composite material is a nano sheet material compounded by a metal organic framework compound and a conductive polymer which is polymerized in situ in holes of the metal organic framework compound, wherein the conductive polymer is formed by doping iodine ions and chloride ions or iodine ions and acetate ions twice. According to the invention, the advantages of high specific surface area, abundant reactive sitesand good conductivity of the conductive polymer of the metal organic framework compound are combined, the metal organic framework compound, the conductive polymer, the iodine simple substance and hydrochloric acid or glacial acetic acid are used as raw materials, the conductive polymer monomer is evaporated to the metal organic framework compound in a gas phase manner, and doping is performed twice. The electrode composite material provided by the invention is used for a supercapacitor electrode, has the characteristics of the large capacity, the good energy storage performance and the high stability and the like, and is simple in preparation process, low in cost and convenient for batch production.