Abstract: For ultra-high pressure oil and gas wells, the test packer has a large upper and lower pressure difference. Due to the simple design structure, the conventional packer has insufficient sealing stability and setting and release ability under extreme working conditions of ultra-high pressure, which is difficult to meet the operation requirements. This paper introduces a kind of CHAMP V ultra-high pressure mechanical setting packer, which can withstand 15000 psi working pressure difference, the highest temperature resistance of 204℃, and has its own bypass, and can be widely used in acidizing fracturing, high salt content, high sulfur content and carbon dioxide gas environment. Through the stress analysis of the string under various conditions, the selection of the appropriate sealing material, setting pressure and control parameters can ensure the stable sealing performance of the packer. The packer has been applied to the X-10 gas well test operation for 5 times with 100% success rate under the condition of ultra high pressure, high temperature, high yield, high sulfur content and high carbon dioxide content. It has very high reliability. It provides reference for similar ultra-high pressure gas wells and special process testing, and has important reference value.