The so-called 'negative difference effect'(NDE) was often defined by the increasing rate of hydrogen evo-lution from magnesium (Mg) surface under anodic polarization.In this work,a series of electrochemical tests and microstructure observations were performed to provide an evidence that the NDE of Mg-Li alloys can be retarded by increasing lithium content.Potentiostatic,galvanostatic and potentiodynamic polarization experiments using Mg-xLi (x =4,7.5 and 14 wt％) alloys electrodes indicated that Mg-4Li alloy maintained the enhancing NDE prior to anodic dissolution as that of conventional Mg alloys.How-ever,the emergence of β-Li phase weakened the NDE of duplex Mg-7.5Li alloy at a low anodic current density,but it was still enhanced apparently after a high applied anodic value (more than 2 mA/cm2).The surface observations,including the plane and cross-sectional morphologies,confirmed that the cracked surface film derived from the anodic dissolution resulted in the catalytic activity of NDE for Mg-4Li and Mg-7.5Li alloys.Furthermore,the NDE of Mg-14Li alloy was suppressed obviously after a prior applied anodic polarization,which was attributed to the persistent and integrated surface film which endured a higher level of applied anodic potential and current.