Epoxy insulators

as the main insulation components

play a significant role in high-voltage gas insulated transmission apparatuses

whose insulation performances are directly related to the electric field distributions along insulator surfaces. Based on the traditional researches on functionally graded insulator

the surface functionally graded material（SFGM） insulator was proposed to regulate the electric field distribution along the insulator surface and to improve the insulation performance of the gas-solid insulation system. Moreover

the fabrication techniques（i.e. centrifugation

3 D printing and flexible casting） and the regulation effects of classical FGM insulators as well as the principle

fabrication techniques and electric field regulation effects of SFGM insulators

were introduced. Graded sputtering

graded fluorination

dip coating and centrifugation techniques were used to achieve functionally graded distributions of permittivity and conductivity on the surfaces of insulators. Compared with the conventional insulators

the fabrication techniques and the mechanical properties of the SFGM insulators are almost unchanged. In the future

SFGM insulators can be used to improve the reliability of ultra-high voltage power transmission systems with much less cost than that of FGM insulators.