The invention relates to a polythene/nylon plastic alloy, a production method and a compatible binder thereof. The production method comprises the following steps: (1) preparing PE-PA compatible binder, that is, preparing mixed solution firstly, namely weighing maleic anhydride, vulcanizing agent DMDBH and grafted second monomer caprolactam according to the proportion, stirring the mixture evenly, then adding diluting agent, stirring the mixture evenly and cooling the mixture to normal temperature to obtain the mixed solution; and then preparing the PE-PA compatible binder, namely after fullymixing high-density polythene, polypropylene and the mixed solution evenly according to the mixture ratio, using a double-screw extruder to carry out reaction extrusion and granulation, so as to obtain the PE-PA compatible binder; and (2) preparing polythene/nylon plastic alloy with low cost and high performance according to an alloy proportion; after mixing evenly the PE-PA compatible binder, the high-density polythene, nylon 66, a dispersant, an antioxidant and a processing assistant, carrying out extrusion and granulation on the mixture by a double-screw extrusion granulating machine, and introducing measured glass fiber subjected to surface treatment in the machining process to obtain HDPE/PA66/GF alloy granules. The polythene/nylon plastic alloy has high performance, low price, and basically can replace pure PA6.