hi Chengqian Zhang, although a late reply, better late than never. try simply to export the bands you want to see in IDL via ENVI's menu: File>export to IDL ... >(name your variable). in IDL you can show a single band image via the line: IDL> tvscl,variable if you export an multi-layered image that way the line in IDL should read: IDL> tvscl,variable[*,*,i] this is assuming that the order of your data in in the format [samples, lines, bands] where i = a specific band that you whish to see. otherwise there's a new program at the RSI code bank of IDL (or ENVI) that is made exactly for that. this is probably even better. i hope this helps. Tal