Abstract: The physiological characteristics of flue-cured tobacco responding to soil moisture content at early growth stage in South Hunan was studied with field experiments, when water supply was controlled at 70%, 50% and 30% of the normal level. The results showed that the leaf development, root development and general growth vigor of the plants watered at 70% and 50% of the normal level were much better than those of the control. For all the treatments, the superoxide anion and hydrogen peroxide in leaves were lower, and the chlorophyll contents were higher comparing with the control; initial fluorescence (F₀) was slightly higher, while the maximum photochemical efficiency (Fv/Fm) was slightly lower than that of the control. The phenomenon of sunburn in leaves of all the treatments was much less than that of the control, which indicated that appropriate control of water supply at the early growth stage was beneficial to the development and growth of vigorous root systems and seedlings of tobacco plants, it could be used as an efficient measure to prevent tobacco from "heat-forced maturity".