Nano-Se/bamboo charcoal (BC) composites were prepared successfully by hydrothermal method. The composites were characterized by SEM, XRD, Atomic Absorption Spectroscopy (AAS) and Atomic fluorescence spectroscopy (AFS) analysis. The effects of the synthesized conditions on the morphologies of Se particles on BC were investigated. The results showed that the reaction time, the adding order of reagents and the concentration of hydrazine have much influence on the formation of nano-Se/BC composites. The application of composites on the keeping fresh of cutting rose flowers was also studied, the experiment results indicate that Nano-Se/BC composites have better effect on the keeping fresh of cutting rose flowers than single BC, Nano-Se, distilled water and commercial "flower food" nutrient solution, the florescence of cutting rose flowers is distinctly extend by Nano-Se/BC composites up to 48 and 24 days in winter and summer respectively. "Synergy effects" and "Delayed release capsule effects" were used to explain the mechanism of Nano-Se/BC composites on the keeping fresh of cutting rose flowers.