Abstract:A study is made of the S1invariant extended solutions of the harmonic maps from a simply connected domain ΩR2 ∪{∞} into the unitary group U(N) (or its real form).S1invariant extended solutions prove to be not only KerAφzinvariant extended solution,but also ImAφzinvariant extended solution.Then another algebraic way to construct S1invariant extended solution is given.It is proved that the extended solution obtained by the flag transformation is also S1invariant. The explicit construction of S1invariant Gextended solution is also presented .