To obtain a polyolefin compsn. which is esp. suitable for producing a calendered film by compounding a mixture comprising a high-density polyethylene and polypropylene in a specified ratio with a specified amt. of an ethylene-α-olefin copolymer.

100 pts.wt. mixture comprising 25-75 wt.% high-density polyethylene and 75-25 wt.% polypropylene is compounded with 1-20 pts.wt. ethylene-α- olefin copolymer. A high-density polyethylene having a melt flow rate (190°C, 2.16 kgf-load) of 0.03-2 g/10 min and an m.p. of 125-136°C is pref.; and polypropylene having a melt flow rate (230°C, 2.16 kgf-load) of 1-13 g/10 min and a m.p. higher than that of the high-density polyethylene, in the range of 130-165°C, is pref. An ethylene-1-butene copolymer and an ethylene-1-hexene copolymer are esp. pref. as the ethylene-α-olefin copolymer.