Board Thread:General Discussion/@comment-33053086-20180323032603/@comment-5430952-20180606033701

Glitchee123z wrote: ......how? Ozpin explained it himself in "Unforseen Consequences.

Ozpin: For thousands of years, I've walked the surface of Remnant, living, dying, and reincarnating in the body of a like-minded soul.

Ozpin: With every rebirth, my soul is eventually merged with another and I am changed, but my memories stay with me.

So basically, when his current body dies, his soul is merged is another with similar ideals to his own. I once had the theory that he was grooming Qrow to become his new body should he have died in Beacon, but it clearly didn't pan out that way, as Oscar became his new host instead.