Abstract: Using Yunyan87,Zunyan6 and k326 as materials, the dynamic changes on secondary enzymes activeness of the three flue-cured tobacco leaves in carbon and nitrogen metabolism were studied. The result showed that, （1）The activity of amylase in all three flue-cured tobacco leaves rose as transplant time went by. After 30th day, the increasing speed of all flue-cured tobacco was faster than before. The activity of amylase in Yunyan87 was highest between 15 and 45 day after transplanting. （2）The Sucrose synthase activity in Zunyan6 was relatively stable in 45 days, in which Yunyan87cut down quickly, at30th day, the lowest, then kept. on the contrary, the Sucrose synthase activity in Yunyan87 went up rapidly. Between 30th and 45th day, which in k326 was lowest. （3）The Invertase activity in Yunyan87 went up slowly at the beginning, and then changing less. In k326, it increased and then decreased, at 15th day, the maximum. The Invertase activity in Zunyan6 did not change much. Between 30 and 45 day after transplanting, Zunyan6 was lower than the other two. （4）The nitrate reductase activity of the three flue-cured tobacco leaves was significantly different, Yunyan87 rose and then stable, but Zunyan6 changed a lot, while k326 went down continuously. At the 15th day, the nitrate reductase activity in Zunyan6 was highest, Yunyan87 and k326 t had no significant difference. At 45th day, Zunyan6 was higher than other, and k326 was lowest. （5）The Phenylalanine lyase activity in Yunyan87 took on an slowly increase and then decreased trend; Zunyan6 and k326 changed in the same trend, up-down-up, but Zunyan6 changed much more than k326. It showed that Yunyan87 had more abilities in secondary enzymes.