To obtain a polyethylene resin compsn. which is suitable for high-speed blow molding and exhibits a decreased swell while retaining good moldability by adding a specified amt. of a fluoropolymer to a high-density polyethylene resin prepd. by using a chromium-based Phillips catalyst.

This compsn. is prepd. by adding 0.01-1 wt.% fluoropolymer to a high-density polyethylene resin. Generally, a homo- or copolymer of a fluoroolefin having a ratio of the number of fluorine atoms to that of carbon atoms of at least 1:2 is used as the fluoropolymer. Polyvinylidene fluoride and polyvinyl fluoride are examples of the homopolymer. Examples of the copolymer are copolymers of fluoroolefins such as vinylidene fluoride, propylene perfluoride, and tetrafluoroethylene, an esp. pref. copolymer being a vinylidene fluoride- propylene perfluoride copolymer.