The present invention discloses a 3-aryl-benzofuranone compound in which R1-R6 in the formula are mutually independent H or C1-C20 alkyls, and R7 is C7-C20 alkyl or C7-C20 mixed alkyl. The present invention also discloses a composition of 3-aryl-benzofuranone compound and the preparation method. The 3-aryl-benzofuranone compound and the composition thereof has the superiority in application due to the characteristics of less proneness to volatilize, less proneness to be extracted, higher resistance to migration and less proneness to bloom and precipitate on the surface of organic materials, and with a wide range of application, it is effective during the application.