The invention relates to an adjustable cable support suitable for a cable with large height difference. The adjustable cable support comprises a plurality of groups of portal frames with different heights; the plurality of groups of the portal frames with different heights are fixedly arranged on the ground at intervals; each portal frame includes two bases, two stand columns and a plurality of cross bracings; the two bases are correspondingly fixed on the ground; the two stand columns are fixedly on the two bases respectively, so that the two stand columns are erected on the ground in parallel; the plurality of cross bracings are connected between the two stand columns at intervals; a plurality of clamps are arranged on the cross bracings; the cable is fixed through the clamps; and therefore, the cable can be fixed in a varied-height difference manner through the clamps on the front and rear portal frames. The adjustable cable support of the invention can be flexibly combined in a large-height difference environment; installation heights, positions and intervals are determined according to the field large-height difference environment; an angle can be automatically adjusted underthe action of gravity; the cable can be fixed at positions of varied different heights; the cable cannot be randomly shifted and has certain heat expansion and contraction margin; and the release of thermal mechanical stress can be realized.