Abstract: By the method of covering with different thickness plastic films to attenuate UV-B radiation, this study investigated the light-response parameters of tobacco cultivar K326 at its early maturity stage when the UV-B transmittance was 100%(CK), 75%(A), 50%(B), 35%(C). The results showed that the net photosynthetic rates(Pn), water use efficiency(WUE) and light use efficiency(LUE) were closely related to UV-B transmittance. When UV-B transmittance varied 35% and 75%, the Pn, WUE and LUE to maintain high states, and we regarded this range of transmittance related to the elevation of Tonghai County was a relative ideal responsive interval of K326. Meanwhile, relative proper PPFD were between 800 µmol/(m2.s) and 1 600 µmol/(m2.s).