Abstract: Three fertilizer formulae (T1, T2 and T3) of various nitrogen, phosphorus and potassium levels were applied to 1, 2 and 3yearold Betula platyphylla seedlings of a halfsib family, respectively, with the objectives of comparing their effects on seedling flowering and fruiting and selecting the optimum one. Then, we investigated the effects of each element (N, P and K) of the optimum formula on growth and development of B. platyphylla seedlings. Results showed that: 1) all formulae significantly increased flowering, compared with no fertilizer (control), with the great response occurring at T3 2) In T3, nitrogen was most effective in improving vegetative growth, making the 3yearold trees reach 3.08 m in height and 25.76 mm in ground diameter, increased by 19.38% and 39.17% respectively than control. 3) Nitrogen fertilizer promoted flowering more effectively than phosphorus or potassium fertilizer. Applying nitrogen improved the flowering rate of 3yearold trees to 49%, compared with only 4%, 1%, and 0 by applying only phosphorus, potassium or without fertilizer. However, applying T3 produced significantly more flowers than applying nitrogen alone, increasing the flowering rate to 90%; 4) During the development from vegetative growth to reproductive growth, some nutrition was allocated for reproductive growth, which reduced the height growth but not diameter growth of the current year.