Abstract: Based on Horton law,this paper proposes the property of tip set of branching networks which is more significant in actual works,and the self-similar dimension of tip set is obtained.Then multifractal nature of tip set of branching networks with two different branching lenghth ratios is described,and its f(α)～α spectrum as well as D_q～q spectrum are analysised qualitatively.Finally,their significance in the real river networks are discussed.