We report a forming-free resistive switching using a solution-processed silicon nanocrystal (Si NC) thin film. A Si NC thin film is formed on an ITO/glass substrate by spin-coating a colloidal Si NC solution in air. The Si NC thin film shows bipolar resistive switching without a forming process. Electrical characteristics at low temperatures and in various gas environments suggest that a non-swichiometric SiOx shell on Si NCs contributes to the resistive switching. We propose that the origin of the resistive switching is a conductive filament of oxygen vacancies on the SiOx shell by an electric field. Published by AIP Publishing.