Polyvinylpyrrolidone (PVP) is an effective surface-capping agent for engineering metal surface structure but is hardly to be thoroughly removed. In this study, the electrochemical treatment was applied for the decontamination of polyvinylpyrrolidone (PVP) on platinum (Pt) nanocrystals. Spherical, cubic, octahedral and cuboctahedral Pt nanocrystals were prepared by the colloidal method with PVP K30 as the capping agent. Electrochemical decontamination of Pt nanocrystals was performed by using square-wave potential steps and methanol electrooxidation was used as a probe reaction. High-frequency potential steps were set up between a high voltage and a low voltage to avoid surface distortion. Cyclic voltammetry (CV) and chronoamperometry measurements were used to evaluate the catalytic activity of the cleaned Pt nanocrystals for methanol. The results showed that electrochemical decontamination was an effective way to clean Pt nanocrystals and the cuboctahedral Pt nanocrystals displayed the best electrocatalytic activity for methanol electrooxidation.