An Ethernet transmission line, comprising: two RJ45 connectors (1, 2), each RJ45 connector (1, 2) having a connection terminal group (10, 20) comprising a first terminal (11, 21), a second terminal (12, 22), a third terminal (13, 23), a fourth terminal (14, 24), a fifth terminal (15, 25), a sixth terminal (16, 26), a seventh terminal (17, 27), and an eighth terminal (18, 28) that are sequentially arranged, wherein the first terminal (11, 21) and the second terminal (12, 22) are a first pair of differential terminals, the third terminal (13, 23) and the sixth terminal (16, 26) are a second pair of differential terminals, the fourth terminal (14, 24) and the fifth terminal (15, 25) are a third pair of differential terminals, and the seventh terminal (17, 27) and the eighth terminal (18, 28) are a fourth pair of differential terminals; and a thin connection line connected between the two RJ45 connectors (1, 2), characterized in that the thin connection line is a multilayer thin film structure, wherein the thin connection line comprises a first flexible printed circuit board layer, a second flexible printed circuit board layer, and a spacing layer, wherein the spacing layer is sandwiched between the first flexible printed circuit board layer and the second flexible printed circuit board layer; the first flexible printed circuit board layer is provided with two first transmission lines, the two first transmission lines being respectively electrically connected to the third terminal (13, 23) and the sixth terminal (16, 26) that correspond to each connection terminal group (10, 20); and the second flexible printed circuit board layer is provided with two second transmission lines, the two second transmission lines being respectively electrically connected to the fourth terminal (14, 24) and the fifth terminal (15, 25) that correspond to each connection terminal group (10, 20); wherein the second flexible printed circuit board layer is provided with two third transmission lines respectively electrically connected to the first terminal (11, 21) and the second terminal (12, 22) that correspond to each connection terminal group (10, 20); and two fourth transmission lines respectively electrically connected to the seventh terminal (17, 27) and the eighth terminal (18, 28) that correspond to each connection terminal group (10, 20), wherein the spacing layer of the thin connection line is further provided with a ground line located between the two second transmission lines and the two first transmission lines. two RJ45 connectors (1, 2), each RJ45 connector (1, 2) having a connection terminal group (10, 20) comprising a first terminal (11, 21), a second terminal (12, 22), a third terminal (13, 23), a fourth terminal (14, 24), a fifth terminal (15, 25), a sixth terminal (16, 26), a seventh terminal (17, 27), and an eighth terminal (18, 28) that are sequentially arranged, wherein the first terminal (11, 21) and the second terminal (12, 22) are a first pair of differential terminals, the third terminal (13, 23) and the sixth terminal (16, 26) are a second pair of differential terminals, the fourth terminal (14, 24) and the fifth terminal (15, 25) are a third pair of differential terminals, and the seventh terminal (17, 27) and the eighth terminal (18, 28) are a fourth pair of differential terminals; and a thin connection line connected between the two RJ45 connectors (1, 2), characterized in that the thin connection line is a multilayer thin film structure, wherein the thin connection line comprises a first flexible printed circuit board layer, a second flexible printed circuit board layer, and a spacing layer, wherein the spacing layer is sandwiched between the first flexible printed circuit board layer and the second flexible printed circuit board layer; the first flexible printed circuit board layer is provided with two first transmission lines, the two first transmission lines being respectively electrically connected to the third terminal (13, 23) and the sixth terminal (16, 26) that correspond to each connection terminal group (10, 20); and the second flexible printed circuit board layer is provided with two second transmission lines, the two second transmission lines being respectively electrically connected to the fourth terminal (14, 24) and the fifth terminal (15, 25) that correspond to each connection terminal group (10, 20); wherein the second flexible printed circuit board layer is provided with two third transmission lines respectively electrically connected to the first terminal (11, 21) and the second terminal (12, 22) that correspond to each connection terminal group (10, 20); and two fourth transmission lines respectively electrically connected to the seventh terminal (17, 27) and the eighth terminal (18, 28) that correspond to each connection terminal group (10, 20), wherein the spacing layer of the thin connection line is further provided with a ground line located between the two second transmission lines and the two first transmission lines.