@GuYan
QtCreator requires a GDB debugger with Python support enabled.
As you are cross- and remote debugging, you need:
gdbserver running on your ARM target
A cross gdb for ARM target archicture with Python support running on your PC
Usually, these gdb's are called arm-angstrom-linux-gnueabi-gdb or similar.
Note that you can also debug from within this gdb, or use the DDD debugger GUI if you can't get it working in QtCreator.