Can I use legacy GUI with new GUI?

I want to use new GUI System with legacy GUI.
When I try to use those, legacy GUI always overlay new GUI.
Can I change layer of legacy GUI and new GUI?
I want to overlay new GUI to legacy GUI.

The new GUI system is objects in the scene, and the legacy GUI is drawn on the screen directly. This means that Legacy GUI will always be drawn infront of anything that exists in the scene, including the new GUI system.

You can do that by setting up the new GUI as Screen Space Camera render mode. Disable the the camera component and then do the render in script after the legacy GUI.

void OnGUI()
{
    if (Event.current.type == EventType.Repaint)
    {
        MyCamera.Render();
    }
}