Abstract: The effects of durations of yellowing and color fixing during curing on chemical components in flue-cured tobacco leaves in a stepping flue-curing barn were investigated. The results showed that:1) When yellowing duration was prolonged for 12 hours, and color fixing prolonged for 9-12 hours, the contents of petroleum ether extract, total N, total sugar, reducing sugar and nicotine and reducing sugar/nicotine (RS/Nic) ratio in cured tobacco samples better matched those required by quality tobacco. 2) Within a certain range, the prolongation of yellowing and color fixing durations increased the contents of malic, citric and total non-volatile organic acids obviously, slightly decreased linoleic acid content; but did not change the contents of oxalic, oleic and linolenic acids obviously. 3) When the durations of yellowing and color fixing were prolonged for 18 and 9 hours respectively, the cured tobacco possessed the highest content of carotenoid degradation products; when the durations of yellowing and color fixing were prolonged for 18 and 12 hours respectively, the cured tobacco possessed the highest content of cembranenoid degradation products; when the durations of yellowing and color fixing were prolonged both for 12 hours, the cured tobacco possessed the highest contents of Maillard reaction products, phenylalanines, neophytadiene and total aroma components. In conclusion, the chemical harmony and aroma quality of cured tobacco leaves were remarkably improved when the durations of yellowing and color fixing were prolonged both for 12 hours.