In this work, the influence of group-velocity mismatch on soliton self-routing pulse switching in a nonlinear fibrecoupler is discussed in detail by the use of both variational approach and numerical simulation. The results obtainedshow that the group-velocity mismatch leads to the relative displacement between the two orthogonal polarizationmodes, increase of the critical power, and reduction of the elimination-light ratio. For sub-ps pulse, the influence cannot be neglected.