Polyolefin resin composition

A method of improving a thermal stability and a discoloration resistance of a polyolefin resin composition which comprises adding (a) 0.01-3.0 parts by weight of an antiblocking agent, the surface OH group content of which is 200 .mu.mol/g or less, (d) 0.01-3.0 parts by weight of a phenol type antioxidant selected from the group consisting of tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 2,2'-methylenebis(4-ethyl-6-t-butylphenol), n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenol) propionate, 4,4'-thio-bis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydrocinnamide), triethylene glycol-bis[3-(3'-t-butyl-5'-methyl-4-hydroxyphenylpropionate] and a mixture of his(ethyl 3,5-di-t-butyl-4-hydroxybenzylphosphate) calcium and PE wax having a weight ratio of 1:1, and (e) 0.01 to 0.2 parts by weight of a phosphite antioxidant to a mixture of 100 parts by weight of the polyolefin resin,

• wherein the cumulative amount of acids having a solid acid acidity pKa or 4.8 or less on the surface of the antiblocking agent is 250 .mu.mol/g or less.