The utility model provides a split expanded-diameter conductor used in an extra-high voltage field test. The split expanded-diameter conductor comprises at least two spacing discs and a plurality of groups of split conductors. Each group of split conductors is composed of at least two sub-conductors. Each spacing disc is correspondingly provided with a plurality of groups of split conductor through holes; a plurality of groups of split conductor through holes are annularly distributed in the spacing disc; wherein each group of split conductor through holes comprises at least two sub-conductorholes, each sub-conductor in the plurality of groups of split conductors respectively penetrates through the corresponding sub-conductor hole in each spacing disc, the at least two spacing discs are fixed on the plurality of groups of split conductors at intervals, and two ends of the plurality of groups of split conductors are respectively fixed through the conductive wire pressing plates. According to the utility model, the equivalent radius of the expanded-diameter conductor can be greatly improved and the surface field intensity of the conductor can be effectively reduced by utilizing a large-small split combination form, the weight of the expanded-diameter conductor is reduced through the matching of special materials and structures, and the expanded-diameter conductor can be used forcarrying out an insulation test and a partial discharge test with extremely strict requirements on corona and partial discharge amount on site.