[quote user="Zhen Li"] I need to generate .r file from a .rsc file[/quote]
You want to reverse-engineer the icon — that is, generate the icon source data from the binary file? Many years ago there used to be such a tool, but I don't think it exists for current versions of MicroStation.
Now that we can use Windows icons, it's more convenient to use one of the many third-party editors for *.ico creation. Some of those editors can use a screen-shot of an existing image as the starting point for a new icon.