Abstract: Piperidinooxyl radical with long-train structure is synthesized. The ESR spectrogram proves that piperidinooxyl radical is produced. The dilatometer tests prove that the piperidinooyl radical with long-train structure performs prominent inhibition role on styrene bulk polymerization initiated with AIBN on 60 ~C. The ultraviolet-visible spectrometry reveals that the piperidinooyl radical with long-train structure strongly absorbs the UV light which will cause the plastic aging and whose wavelength is between 230-350 nm. TG analysis shows that the piperidinooyl radical with long-train structure are quite stable at high temperature. The results indicate that the piperidinooyl radical with long-train structure is capable of being used as a kind of plastic additive with good anti-aging performance.