  Vector-like quarks (VLQs) are attractive extensions to the Standard Model.
They mix with the SM quarks and can lead to rich phenomenology. Determination
of VLQ's interaction structure with the SM is then an important issue, which
can be inferred from the decay products of VLQs, such as top quark. We
calculate the spin-analyzing powers for charged leptons from top quark in VLQ
decay for various VLQ scenarios. We find that the top polarization effect will
be helpful to distinguish different natures of the VLQ couplings with the SM.
