PURPOSE: To obtain the title composition consisting of a polymerization inhibitor selected from isopropenylacetophenone, 4-methoxyphenol, 4-hydroxy-2,2,6,6- tetramethylpiperidinoxy, etc., and used as a resin raw material capable of storing for a long period.

CONSTITUTION: The aimed co/position consisting of at least on kind of polymerization inhibitor selected from a group consisting of isopropenylacetophenone, 4-methoxyphenol, 4-hydroxy-2,2,6,6-tetramethylpiperidinoxy and N- nitrosophenylhydroxylamine ammonium salt. The content of polymerization inhibitor in the composition is 10-10000ppm, preferably 20-2000ppm. The title composition may be further blended with a diluent (e.g. phenol or hexane) and blend amount of the diluent is normally 10-80wt.%, preferably 40-60wt.%, based on the title composition. The blending temperature is 20-60°C.