The invention provides a copper nanowire and a preparation method thereof. The preparation method comprises the following steps that in the environment with the dew point no more than -50 DEG C and the oxygen content mo more than 10ppm, lithium metal is heated to 200-800DEG C, and therefore the lithium metal is in the molten condition; copper is added in to the lithium metal in the molten condition, heat preservation is conducted and lasts for 5-15min, and mixing is conducted to form molten alloy; the molten alloy is cooled to the room temperature, and lithium-copper alloy is manufactured; andthe lithium in the lithium-copper alloy is removed, and the copper nanowire is manufactured. The copper nanowire is manufactured by a single method, the temperature in the preparation method is low,and the shape and appearance of the copper nanowire can be controlled. In addition, the cost of the preparation method is low, and the copper nanowire can be prepared at a large scale. The prepared copper nanowire can be used as a three-dimensional fluid collector of a lithium battery, and can be directly used in the fields of transparent conductive films, conductive ink and the like.