Abstract: With‘Xiangyan 3’as experimental material, effects of PP₃₃₃ application on the strong seedling cultivation in flue-tobacco were studied. Tobacco seedlings were treated with different concentrations of PP₃₃₃ when the plants were at the three to four leaves stage, the agronomic traits and physiological characteristics were tested. The results showed that the plant height and the maximal leaf area decreased obviously, the stem diameter, root- shoot ratio and dry- fresh ratio increased with the use of PP₃₃₃; while the root activity, chlorophyll and soluble sugar content of tobacco seedlings were enhanced extremely significant, the activities of SOD and POD were improved obviously, the level of MDA reduced. The comprehensive characteristics of tobacco seedlings were the best while the seedlings were treated with 100 mg/L PP₃₃₃. Compared with the CK, the plant height and the maximal leaf area decreased 3.2 cm and 17.7 cm2, respectively; the stem diameter, root-shoot ratio, dry-fresh ratio increased by 12.1%, 56.1% and 24.7%, respectively; the root activity, the content of chlorophyll and soluble sugar increased by 50.8%, 41.9% and 33.0%, respectively; SOD and POD were enhanced by 0.38 and 0.32 times; MDA reduced 1.687 nmol/g. In conclusion, the application of PP₃₃₃ could effectively inhibit the growth of the aerial part, promote the growth of roots, make the root grow in harmony with the aerial part, and was beneficial to cultivate healthy seedlings.