Abstract: The result of pruning on 2～5 years old Paulownia trees without natural trunk extension showed, the effective way to promote trunk extension and its growth is to pruning the top branches and part of branches of lower canopy. The optimum pruning applications should be conducted in spring 3 years after plantation, under 50%～70% of pruning strength and leaving 2～3 layers of side branches. The successful rate of trunk extension by this method is 97.5% with the result of its height, diameter and form quotiety (FQ) of 5.7m, 104cm and 0.59, respectively; which had less effectives of affecting the growth of branches and the stock, but had much more effectiveness of promoting the growth of upper trunk and stock of the main trunk, with the result of reducing the FQ of the formal trunk. Under the treatment of pruning on low seedling with comparison of CK of high seedling, the height of the trunk is 71.7% higher than that of CK. After 2～3 years growth, the extension part combined well with the formal trunk whose stock reached 27.1%～32.3% of the whole volume. Compared with CK, there was no significant change of the growth of formal branches of lower canopy and its volume, on the other hand, the growth of the upper branch and standing stock of main trunk is 7.2%～8.5%, 42.2%～45.6% higher than that of CK, respectively; the treatment reduced the tapering grade, and at the same time enhanced the FQ.