The interfacial behavior between waterborne polyurethane (WPU) electrolyte and lithium was investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA). CV results between -3V and 3V show three peaks on the positive sweep and two peaks on the negative sweep, indicating that the lithium stripping process is quite different from its depositing process. A series of schematic diagrams of interfacial phenomena between WPU electrolyte and lithium metal is proposed to help in interpreting the CV results. Based on the LSV and CA results, our prepared WPU electrolyte showed the electrochemical stability up to 4.25V and the pendant anions do not affect the long term polarization of this electrolyte.