Hi I m new for unity engine, Can i use flash Actionscript 3.0 for creating unity application???
You can't, no
UnityScript is very similar to ActionScript 3 though. For example, on this page, once you disregard the "package" stuff that isn't needed in Unity, nearly all that ActionScript code would compile as UnityScript just fine with only really minor syntax changes (replace "trace" with "print", "Boolean" with "boolean", etc.).