The multigraft copolymer (A(2)B(2))(5), consisting of 10 side-chains (A blocks) regularly grafted on the 5 points of a backbone (B blocks), has been theoretically investigated by using self-consistent mean-field theory (SCMFT). We discussed the length scale of self-assembled morphologies and the corresponding phase transition sequences at different factors, including interaction parameter (chi) and volume fraction of A blocks. The free energy of formed nanostructures is a quadratic function of box size, leading to the identification of length scale at different conditions by the minimization of free energy with respect to box size. Moreover, by comparing the free energy between different phases, we observed a phase transition sequences, D -> C -> G -> L -> O-70 -> G -> C -> S -> D, which is consistent with that of simple diblock copolymer. However, this transition sequence changes as the variance of chi N and f(A). Finally, we constructed the phase diagram of this multigraft copolymer with respect to chi N and f(A), where O-70 was found to possess a larger region. Our calculated results show great guidance for the experimental study on the multigraft block copolymer.