Abstract: The effects of topping and NAA(plant growth regulator) application after topping on dry-matter accumulation,nicotine synthesis and K absorption in tobacco plant were studied.The results showed that NAA application after topping promoted dry-matter accumulation,K absorption and K utilization in tobacco and reduced nicotine synthesis and K loss from leaves at later growth stage.Although the amount of total dry-matter in tobacco plant which was not topped did not decreased,the dry-matter and nicotine accumulation in leaf,K absorption,and utilization reduced obviously.