Orthogonal　frequency　division　multiplexing　(OFDM)　is　an　attractive　modulation　candidate　for　Cognitive　Radio　(CR)　networks.　Effective　and　reliable　subcarrier　power　allocation　in　OFDM-based　Cognitive　Radio　(CR)　networks　is　a　challenging　problem.　This　paper　focuses　on　the　power　allocation　for　OFDM-based　Cognitive　Radio　(CR)　networks.　Our　objective　is　to　maximize　the　total　transmission　rates　of　Secondary　Users　(SU)　by　adjusting　the　power　of　subcarrier　while　the　interference　introduced　to　the　Primary　User　(PU)　is　within　a　certain　range　and　the　total　power　of　subcarrier　is　not　beyond　the　total　power　constraint.　We　investigate　the　optimal　power　allocation　algorithm　for　OFDM-based　Cognitive　Radio　(CR)　based　on　convex　optimization　theory.　Then,　because　of　high　complexity　of　the　optimal　power　allocation　algorithm,　we　propose　an　effective　suboptimal　power　loading　scheme.　Theory　analysis　and　simulation　results　show　that　the　performance　of　the　suboptimal　power　allocation　algorithm　is　close　to　the　performance　of　the　optimal　power　allocation　algorithm,　while　the　complexity　of　the　suboptimal　power　allocation　algorithm　is　much　lower.　©　2010　Science　Press,　Institute　of　Electronics,　CAS　and　Springer-Verlag　Berlin　Heidelberg.