Abstract: Five different doses of UV-B radiation was supplied to tomato(Lycopersicon esculeutum Mill)with the doubled CO₂ concentration(700μmol ·mol^-1)in winter plastic greenhouse.The influences on the seedling growth,fruit quality and yield of tomato were investigated.The results showed that the seedling growth,and the contents of UV absorbing compounds,soluble sugar,origanic acid,Vc,lycopene of tomato fruits,and yield of tomato increased under doubled CO₂ concentration.Under the doubled CO₂ concentration the effects of lose doses of UV-B radiation could promote the effects of doubled CO₂ concentration furtherly.But there is not significant difference on yield of tomato.The dose of UV-B radiation(about) 1.163 kJ·m^-2 is the best dose.When the dose of UV-B radiation is more than it,the effects of UV-B will be reduced.