The sequence parameters and unbalance factors of six-circuit transmission line with two shield wires on the same tower are computed. Firstly, sequence parameters of six-circuit transmission line are analyzed based on Carson model and image method correspondingly. Secondly, the unbalance factors of six-circuit transmission line are defined in detail. Finally, take a 110kV six-circuit transmission lines as an example, the sequence parameters and unbalance factors are computed using MATLAB. Through comprehensive comparison, the unbalance factors especially through-type electromagnetism unbalance factors for inverse phase sequence are smaller than others. Inverse phase sequence is recommended as the optimum arrangement.