The invention relates to a preparation method of high density polyethylene resin special for abnormal-shape bottles; in a granulation workshop section of a high density polyethylene device, 0.01-0.8% by mass percentage of a composite processing additive is added for direct preparation of the high density polyethylene resin special for the abnormal-shape bottles; the composite processing additive is prepared from the following substances: by mass, 10-20% of an antioxidant, 35-50% of a lubricant, 20-30% of a fluorine elastomer and 15-20% of oxidized polyethylene wax; the resin has the characteristics of moderate melt strength and wide molecular weight distribution, and the characteristics are necessary for a special material suitable for blowing the abnormal-shape bottles; the resin has excellent processing performances, and solves the problems that: during production of the abnormal-shape bottles by use of blend resin, the produced abnormal-shape bottles have unsmooth surfaces and uneven wall thickness, articles contained in the abnormal-shape bottles may produce peculiar smell, and the like.