By using the theory of fractal geometry, five dominant tree species in north-facing slope of mountain of northern Hebei were chosen to investigate fractal dimension of the crown and box-counting dimensions of branches. The results indicated that: (1) The widest crown of Larix principic-rupprechtii were in the middle and upper part of the crown(about 60%-80% of the total height), those of the B.platyphylla in the middle part (40%-60%), those of the Pobulus davidiana and Tilia mandschurica both in the mid-lower parts (40%-50%). Those of the B.davurica of Larix principic-rupprechtii -B.platyphylla-B.davurica appeared in the upper part (70%-80%), while those of the B.davurica of Pobulus davidiana-B.platyphylla-B.davurica in the middle part (50%-60%); (2) Fractal dimension of Larix principic-rupprechtii crown structure was 1.690, which was the biggest, meanwhile fractal dimension of four kinds of trees in Pobulus davidiana-B.platyphylla-B.davurica were about the same from 0.770 to 1.202, while in the two mixed forest, the fractal dimension of the B.platyphylla in the former(0.997) was similar to that of the latter(1.149), about B.davurica, fractal dimension(1.257) in the former larger than those(0.770) in the latter. (3) Branching orientation of Larix principic-rupprechtii of 13.1 in DBH were homogeneous distribution both in every direction and on the whole sample, in addition, branches of B.davurica 15.8 in DBH of the former were homogeneous distribution in most direction. However, at different tree ages, branches of B.platyphylla of the former and the four kinds of trees of the latter were inhomogeneous distribution in every direction. (4) As tree age increasing, branching angle of Larix principic-rupprechtii varied from 85° to 95°, while those of Tilia mandschurica distributed from 55° to 85°. Branching angles of Pobulus davidiana at younger and elder tree age were from 40° to 55°, but at middle age from 60° to 80°. Also, the branching angle of B.davurica were from 30° to 65°. In the former, branching angle of B.platyphylla ranged from 25° to 90°, while in the latter from 45° to 85°. (5)The average fractal dimensions of Larix principic-rupprechtii branching patterns was the highest which was up to 1.772, and was followed by that of four kinds of trees of Pobulus davidiana- B.platyphylla-B.davurica. However, the value of B.davurica between the two mixed forests were different significantly, which was 1.476 in the former and was 1.674 in the latter. Although the branches of same species were different in shape and size, there were no significant difference between each other, and their correlation coefficients were all above 0.93, which indicated that the various branching pattern had the self-similar commonality.