The present invention relates to heterodimeric conjugates of neomycin-chloramphenicol, of formula 1, their preparation and their use. Because of their heterodmieric structure, they can recognize both stem and loop of RNA motif and show binding ability to a certain RNA such that they have an enhanced pharmaceutical efficacy and reduced side effect which can be caused by non-specific drugs. For these reasons, they can be effectively used as an antiviral agent, an antibacterial agent or an anticancer drugs.