Abstract: An ultra-high expansion downhole packer includes an anchor, a primary expansion cone, and a central tube. The anchor is provided with a first tapered through-hole having a large end sleeved at a small end of the primary expansion cone. The anchor is radially expandable to anchor with an inner wall of a wellbore. The primary expansion cone is provided with a second tapered through-hole, and the second tapered through-hole has a large end sleeved at a small end of the central tube. The primary expansion cone is a radially expandable structure, and the primary expansion cone supports the anchor after an expansion. The primary expansion cone is provided between the anchor and the central tube. The primary expansion cone is first driven into the anchor to make the anchor radially expand, and then the central tube is driven into the primary expansion cone to make the anchor radially expand again.