Enable natural scrolling in xfce4

- Run /usr/lib/gnome-settings-daemon/gnome-settings-daemon.
It can be enabled in Settings -> Session and Startup -> Autostart -> GNOME Settings Daemon

- In dconf-editor find touchpad.
It can be in org.gnome.settings-daemon.peripherals.touchpad or in org.gnome.desktop.peripherals.touchpad.
Enable natural-scroll option.

- Reboot

Note:
reverse scroll direction option in System Settings should be disabled in my case