There are disclosed a polyolefin resin composition, containing (A) an organic peroxide, (B) a phosphorous type anti-oxidant of formula (I): wherein R represents C1-8 alkyl, C5-8 cycloalkyl, C6-12 alkylcycloalkyl, C7-12 aralkyl, or phenyl, (C) anti-oxidant of formula (II): wherein R1, R2, R4 and R5 independently represent hydrogen, C1-8 alkyl, or the like, R3 represents hydrogen, C1-8 alkyl, X represents a single bond, sulfur atom, or the like, and (D) polyolefin resin, and wherein the amounts of (B) phosphorous type anti-oxidant of formula (I) and (C) anti-oxidant of formula (II) each is 0.001 to 1 part per 100 parts by weight of the total amount of (A) and (D), and a production process thereof.