Abstract: In order to use the technology of seedling transplant under plastic mulching, a comparison experiment was conducted to invesitigate the physiological effect. The results indicaded that the pattern of seedling transplant under plastic mulching was better than convertional pattern in several aspects. Cation exchange capacity (CEC) of roots improved 1.37 times, 1.50 times, 1.51 times than CK at the stages of resettling, fast-growing, and mature, respectively, all of the difference reached significant level. Activity of nitrate reductase (NR) was improved 1.4 times, 1.31 times, 1.49 times than CK at the stages of resettling, fast-growing, mature, respectively. Activity of invertase (Inv) improved 1.2 times, 1.4 times, 1.4 times than CK at the stages of resettling, fast-growing, mature, respectively. Root dry matter was 2.7 times, 1.4 times, 1.2 times than CK at the stages of resettling, fast-growing, mature, respectively, the difference reached significant level at resetting stage. Leaves dry matter was 1.3 times, 1.1 times, 1.3 times than CK at the stages of resettling, fast-growing, mature, respectively, the difference reached significant level at budding time. Neutral aromatic components in the tobacco leaves improved obviously, the total content of carotenoids degraded products which had the major influence to aroma quality was improved 1.51 times than CK especially, and the content of solanone which belonged to cembraneoids was improved 1.47 times. The quality indices of the chemical components in tobacco leave were more close to the standard of high quality tobacco.