The　concept　of　cognitive　radio　(CR)　is　proposed　to　deal　with　the　problem　that　the　spectrum　resource　is　almost　used　up　but　some　licensed　bands　are　under　very　low　utilization　at　the　same　time.　In　CR　networks,　secondary　users　(SUs)　are　allowed　to　utilize　the　licensed　spectrum　bands　by　paying　to　the　primary　users　(PUs)　with　the　spectrum　licenses.　Besides,　with　the　rapid　development　of　wireless　communications　and　portable　user　devices,　power　consumption　issues　draw　more　and　more　attentions　recently.　In　this　paper,　taking　into　consideration　the　power　consumption,　we　proposed　an　optimal　resource　allocation　scheme　to　maximize　PU＇s　reward　in　green　CR　networks.　SUs＇　SNR　requirements　and　interference　limit　are　considered　in　the　optimal　resource　allocation　process.　We　use　restless　bandits　formulation　to　reduce　the　computational　complexity.　In　addition,　the　simulation　results　show　that　the　proposed　scheme　improves　the　reward　of　PU　compared　to　greedy　scheme　and　the　existing　scheme.　©　2013　IEEE.