The invention discloses a method for improving the afforestation quality of Alnus formosana. The method includes the steps of: bud seedling cultivation, seedling cultivation in light substrate containers, forest land clearing and land preparation, seedling planting for afforestation, seedling checking and complementary planting and young forest cultivation, wherein two-stage seedling cultivation is adopted, roots of bud seedlings are trimmed before transplanting is conducted, and seedling cultivation by using the light substrate containers and root pruning by air are adopted, so that growth ofmain roots is inhibited, multi-level lateral roots are promoted to grow so as to form a large number of root balls, and the stress resistance is strong; when the seedlings grow to a height of 15-20 cm, the seedlings can be taken out from the containers and used for afforestation, the period of seedling cultivation is shortened, the production cost is saved, the production efficiency is improved,and large-scale, specialized and industrialized production is achieved; the seedlings has a small transpiration area, a high water content is maintained in the seedling bodies and substrates, and theseedlings with bags are transplanted, so that no damage to the roots is caused, growth begins as soon as the seedlings is transplanted in soil, no recovery periods is achieved, and the survival rate of afforestation is 95% or above; the seedlings have no mechanical damage, obvious apical dominance and rapid growth, and is beneficial to cultivation of trunks, so that high-quality, fast-growing andhigh-yield forests are cultivated.