The invention provides a coating preparation method for an iron-based electric arc spraying coating with the high thermal conductivity, belongs to the field of thermal spraying in material machining engineering, and particularly relates to a preparation method for a cored wire and the coating of the cored wire by using electric arc spraying, wherein the cored wire is high in thermal conductivity and good in mechanical property. A powder core comprises the following ingredients of, by mass, 15-26% of high carbon chromium iron powder, 26-52% of boron iron powder, 2-10% of number 75 ferrosiliconpowder, 8-18% of chromium carbide powder, 1-5% of electrolytic manganese powder and the balance reduced iron powder; the wire is prepared through rolling after evenly mixing according to a certain mass ratio; and a strip material used by cored wire outer skin adopts a 430 stainless steel strip, and the filling rate of the cored wire is 28-32%. When electric arc spraying is used to prepare the iron-based coating with the high thermal conductivity, the spraying technology adopts voltage being 28-32 V, current being 180-220 A, the spraying distance being 180-220 mm and compressed air pressure being 0.4-0.6 MPa. According to the coating preparation method for the iron-based electric arc spraying coating with the high thermal conductivity, the iron-based coating with the high thermal conductivity and hardness can be obtained.