The invention provides a preparation method of a zinc-aluminium seamless flux-cored wire. The method provided by the invention is characterized by comprising the following steps: smelting raw materials such as zinc, aluminium and the like, and casting the melt into an ingot; after riser removal and scalping, putting the ingot into a nitrogen protection furnace and carrying out shpheroidizing annealing in the nitrogen protection furnace at 180-230 DEG C for 1-2 hours; blending a core flux into paste by virtue of an organic solvent and filling the paste in a pressure injector; then putting the zinc-aluminium alloy ingot into a dedicated extrusion die, connecting the die to the pressure injector, and starting the extrusion die to directly extrude welding wire which has the diameter phi of 5.0-12.0mm and has a core of the flux and a sheath of the zinc-aluminium alloy; and then performing drawings many times to obtain the finished product. The flux-cored wire manufactured by the method is characterized in that the flux is filled continuously and evenly; during the use process of the flux for welding, no welding slag is left, no carbon is deposited, the operation is convenient, and the production efficiency is high, therefore, the problems such as complex processing steps, high cost and the like in the prior art are solved.