A facile in situ template carbonization method was developed to prepare bismuth nanocrystal-filled carbon nanotubes (Bi-CNTs). The resultant Bi-CNTs exhibited high photoactivity for the Rhodamine B (RhB) degradation under UV irradiation, and the degradation efficiency was up to 96.6% after 120 min. It was proposed that the surface plasma resonance of Bi nanocrystals may be related to photocatalytic activity of Bi-CNTs under UV irradiation.