I used B&K AVR-505 AV Receiver.And which Speaker suitable for B&K AVR-505.Please can anyone tell me ?

That receiver has a pretty robust amp and should handle just about any speaker system out there, a lot depends on your room how large it is what type of acoustic signature it produces what type of listening your going to do...how close and how loud you listen....type of music etc... if you live in the states I would recommend taking a loo at Aperion or maybe Paridgim speakers...UK Waferdale; Tannoy Canton, Australia Dali Speakers and there are many others available in different local...

Nearly any speaker is suitable. I personally would go with something from Mirage, as their high end model is currently on a STEEP discount close out.