[en] In our previous work [Phys. Rev. D 70, 037503 (2004)] for the e⁺p→tν+X process, we have shown that the top quark possesses a high degree of spin polarization when its spin decomposition axis is along the incoming lepton beam. In this work, the potential of ep collisions to probe an anomalous Wtb vertex is investigated via the polarized single top quark production process for TESLA+HERAp energy. The effects of the top quark polarization to Wtb couplings F_2L and F_2R are discussed. It is possible to define a polarization axis for the top quark that is more sensitive to new physics than the unpolarized case