Does anybody know if QTP Plug-In can Identify UI objects that was built by Flash Catalyst.
Not by default... you'll need to do some additional programming.
Within the Flex 4 documentation http://help.adobe.com/en_US/Flex/4.0/TestingQTP/flex_4.0_testingqtp.pdf
It says: Flex documentation for developers includes a set of guidelines for creating testable applications. These guidelines include instructions on how to compile testable applications, instrument custom components so that they can be tested, and write applications so that the testing process works more smoothly.
Search for Instrument Custom Components is listed here: http://help.adobe.com/en_US/flex/using/WS2db454920e96a9e51e63e3d11c0bf69084-7ec5.html