I am referring here to the original Walt Disney movie. Do anyone knows which type of flute is used in this song?
If you are referring to this, it sounds like a bass flute, or probably just an ordinary flute playing at the very low end of its range.
I doubt it's a bass flute. (Bass flutes are much, much lower) More likely an alto flute, https://en.wikipedia.org/wiki/Alto_flute.
The low range on the part is very robust, which wouldn't sound as powerful on a standard flute; The alto can push more sound.