This　paper　presents　a　scheme　for　realizing　the　frequency　up-conversion　between　two　collective　atomic　modes.　In　the　scheme　two　atomic　samples　are　coupled　to　a　cavity　mode.　Under　the　large　detuning　condition,　the　two　collective　atomic　modes　are　coupled　via　the　virtual　excitation　of　the　cavity　mode　and　the　effective　Hamiltonian　corresponds　to　the　frequency　up-conversion.　In　the　scheme　the　cavity　mode　is　only　virtually　excited　and　thus　the　process　is　insensitive　to　cavity　decay.　©　2009　Chin.　Phys.　Soc.　and　IOP　Publishing　Ltd.