Abstract: Using lacquer seed oil as raw material, sodium caseinate as emulsifier, nanoemulsion of lacquer seed oil was prepared by high pressure homogenization, the optimum preparation conditions of nanoemulsion of lacquer seed oil were deter mined by single factor test; the storage stability of lacquer seed oil under different temperature was investigated; the antioxidant activity was evaluated; in vitro cellularmethod was used to investigate the anti-UV radiation activity of lacquer seed oil nanoemulsion. Results showed that the optimum preparation conditions of lacquer seed oil nanoemulsion were the mass fraction of emulsifier 2.5%, the mass fraction of lacquer seed oil 6%, homogeneous pressure 100 MPa, homogenization 4 times, the resulted nanoemulsion showed average particle size of 163.0 nm, Zeta potential of -41.01 mV, polydispersity index (PDI) of 0.225, and good storage stability, the average particle size could keep within 200 nm under storing for 30 d at 4, 25, 60 ℃. The median effective concentration (EC₅₀) values of DPPH, ABTS and hydroxyl radicals were 24.26, 23.77 and 21.10 mg/L, which showed better antioxidant activity than positive control vitamin C(38.48, 43.25and 40.56 mg/L). Lacquer seed oil nanoemulsions had significant repair effects on NIH 3T3 cells with ultraviolet A (UVA) radiation damage, the survival rate of UVA damaged NIH 3T3 cells was higher than 100% when the mass concentration of nanoemulsion was more than 5 mg/L, which indicated that lacquer seed oil nanoemulsion had good anti-UV radiation activity.