Provided is a method for grafting a large branch. According to the method, the large branch is cultivated to send forth roots, a disc is fixed to an upper trunk part and then bound into a barrel through a straw bag or a plastic net, the barrel contains fertilizer and mud for cultivating the roots, and when the roots can completely support growth of the large branch, the 30-60-centimeter lower portions of the long roots of the large branch are sawed off; a long slope is formed on a lower trunk part under the roots, and the length of the slope is 2-5 times greater than the diameter of the lowertrunk part; a same long slope is formed on the portion, where the branch is grafted, of the lower trunk part, the two slopes are flush with each other, the bark of the upper trunk part is flush with the bark of the lower trunk part, and the bark of the upper trunk part and the bark of the lower trunk part grow independently and circularly; in the later growth period, liquid in the two kinds of woods can be cycled with each other, the two kinds of bark can grow into a whole part, wood layers sent forth by the bark also grow into a whole part and are thick, the roots on the upper surface are slowly removed step by step, and then an integral tree is formed. Moreover, other different kinds of branches can also be grafted on the same tree, and then an ornamental tree which can send forth different kinds of leaves, flowers and fruits is obtained.