A quick note for the following problem, cus I experienced these problem 2 times, if I don't write this down, I think I will experience third times when I reinstall ArchLinux next time....
1. QT applications looks weird(icon and interface) on Gnome.
$ sudo pacman -S gtk-qt-engine
2. Cursor changes when it hover QT applications in Gnome
It's easy to solve this problem, just create a symbol and link it to your cursor theme.
$ cd /usr/share/icons
$ sudo ln -s YOUR_CURSOR_THEME default