Abstract: A field experiment was conducted to study the effect of different transplanting days on main growth and development, contents of nitrogen and potassium in tobacco leaves at maturity stage, economic traits of flue-cured tobacco in order to elucidate the best transplanting period of flue-cured tobacco cultivar Qinyan96 in Longxian. The results showed that with postponement of transplanting date of flue-cured tobacco, all main growth dates were put off; field growth period after transplant became shorter. Agronomic traits, the contents of nitrogen and potassium, yeild, output value and proportion of superior tobacco of flue-cured was ascend in first and descend under postponement of transplanting period. Based on comprehensive analysis, the effect of 6/5 treatment was best, and it's economic traits was better than that from orther treatments. Hence May 10 was the best appropriate transplanting date of Qinyan96 in Longxian. All the results indicated that Appropriate transplanting period provide suitable climatic conditions for flue-cured tobacco, then improve nitrogen, potassium nutrition of tobacco leaves at maturity stage and increase dry matter accumulation resulting in better yield and quality of flue-cured tobacco leaves.