Script for Unity Engine???

Hi I m new for unity engine, Can i use flash Actionscript 3.0 for creating unity application???

You can't, no

Currently the only supported languages are C#, UnityScript (a JavaScript dialect) and Boo

No.

http://unity3d.com/unity/features/scripting

"Unity supports three scripting languages: JavaScript, C#, and a dialect of Python called Boo."

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.).