The mediation of metastable state has been approved to be a promising tool to achieve giant modulations of the physical properties in artificial structures. In this work, the metastable state La0.67Sr0.33MnO3 (LSMO) films with the coexistence of two phases were fabricated on the tensile ferroelectric BaTiO3 (BTO) substrates. Upon application of pulse electric fields to the BTO substrates, the oxygen vacancies and charge redistribute and result in giant and volatile electroresistance (~230%) and normal and nonvolatile electroresistance (~5%) in the LSMO films, respectively. The observation of binary resistance states is very interesting and totally un-expected, since only a normal electroresistance has been reported in the similar LSMO/piezoelectric structures previously. Here, we attribute the binary state performance to the model of oxygen redistribution and charge accumulation/depletion modulated by the ferroelectric field effect. The oxygen redistribution strongly affects the double exchange interaction in the LSMO layer, which leads to the giant and volatile electroresistance. This work indicates that the mediation of metastable states by electric field is a promising way to enrich the physical properties in artificial structures.