Purification and length separation of oxidatively shortened single-walled carbon nanotubes (SWNTs) were achieved by size exclusion chromatography (SEC) without assistant reagents for dispersion. Almost all the carbonaceous impurities, such as carbonaceous particles, graphene fragments, can be removed from the oxidatively shortened SWNTs materials. The short carbon nanotubes were separated into fractions according to nanotube lengths, and the length distribution of each fraction was relatively narrow.