The invention discloses a high-alumina direct current porcelain insulator. The insulator comprises, by weight, 10-15 parts of smolmitza, 1-5 parts of high-alumina bauxite, 30-40 parts of alumina, 5-10 parts of white plaster, 5-10 parts of potassium feldspar, 10-20 parts of Jinyang soil and 15-25 parts of Bo'ai clay. The porcelain insulator is good in mechanical performance and low in production cost, process control is easy, and the high-alumina bauxite and the smolmitza are used, so that the ball milling time is shortened, the cost is reduced and the process performance is improved. According to the insulator, 5-10% of low-sodium potassium feldspar is introduced, and the Na content in chemical components of a semifinished product is less than 0.2%, so that the insulator breakage caused by local swelling stress generated during migration of alkali metal sodium ions in an electrical porcelain material can be prevented, and simultaneously, the problems that the insulator is broken down under the long-term action of a direct current field due to the fact that electric fields are not distributed evenly caused by conducting layers of different specific resistance, which are formed inside a porcelain part during ion migration, can be solved.