The invention discloses a medium-voltage overhead trunk power distribution network construction structure which comprises a knot-type wiring structure, at least two graftable wiring structures and at least two separatable wiring structures, wherein one of the graftable wiring structures is arranged between each two separatable wiring structures, and the medium-voltage overhead trunk power distribution network with a three-sectioned and three-linked whole-group power supply unit structure is built. The invention also discloses a building method for the medium-voltage overhead trunk power distribution network construction structure. Compared with the prior art, the medium-voltage overhead trunk power distribution network construction structure has the advantages that the independent three-sectioned and three-linked structure is contained and participated in building intra-station or inter-station communication of link lines with a home station or other substations, mutual link lines are not from the same bus of a substation, no more than two link points of the same line is required, and power supply capability to non-fault sections can be still ensured when a fault occurs in the line or a fault occurs during access of a power supply to the bus.