The invention belongs to the technical field of novel function nanometer material preparation, and discloses a preparation method for a copper nanowire. Reducing agent is added to copper source on the premise that morphology control agent and chemical potential control agent are exist in water solution, and the copper nanowire are obtained after separation and under the condition that reaction is carried out for at least one hour in temperature of 25 DEG C to 100 DEG C, wherein the copper source is one or combination of copper hydroxide and copper oxide, the morphology control agent is one kind or combination of more than two kinds of polyethylene polyamine, the chemical potential control agent is one or combination of sodium hydroxide and potassium hydroxide, and the reducing agent is one or combination of hydrazine hydrate and hydroxylamine. The preparation method for the copper nanowire has the advantages of being simple in technology and device, cheap and easy-getting in raw materials, low in cost, high in productivity, suitable for large-scale industrial production, and the like. Prepared copper nanometers are uniform in diameter, diameters and lengths of the copper nanometers can be controlled through changing concentration of the morphology control agent and concentration and reaction temperature of the copper resource.