Abstract: Effects of the step-temperature yellowing curing technology on polyphenol, related enzyme activities and nitrogen compounds in tobacco leaves were studied using electric-heated flue-curing barn. The results showed that contents of total phenols, chlorogenic acid, caffeic acid and rutin increased during all bulk curing processes. Total phenols and chlorogenic acid contents of the step-temperature yellowing technology were higher than control except at the muscle-yellowing temperature stage. The contents of caffeic acid, rutin and scopoletin changed differently between the two technologies, but little difference was detected at the end of curing. Lower Polyphenol oxidase(PPO)activity during the sensitive period of the brown reaction and significantly higher Peroxidase(POD) activity during curing were observed for the step-temperature yellowing technology. With the step-temperature yellowing technology, the changes of phenylalanine and tyrosine of the showed a down-up-down trend during curing, lower proteins content and higher phenylalanine and tyrosine contents in middle and late curing period were observed. In short, the step-temperature yellowing technology was beneficial in improving the contents of total phenols, chlorogenic acid and aroma values, and was also favorable to protein decomposition and accumulation of phenylalanine and tyrosine.