The utility model discloses a force transmission device which includes two semicircle-disk-shaped members which have specific thickness and can be combined to form a cylinder. Grooves which pass through the semicircle-disk-shaped members in the thickness direction are formed on respective combination faces of the two semicircle-disk-shaped members. After the two semicircle-disk-shaped members are combined, the two grooves are combined so that a smoothly transiting combination hole is formed. The combination hole can be fastened in an installation hole of a tension sensor. During installation, a side wall of part of the combination hole in the installation hole is in close fit in a face-contact method with the inner wall of the installation hole. Outer grooves are formed on respective outer arc parts of the two semicircle-disk-shaped members along the outer circumferences. When the two semicircle-disk-shaped members are combined to form the cylinder, the outer grooves on the two semicircle-disk-shaped members in the outer circumference direction of the cylinder transit smoothly and the sections of the outer grooves are arcs. During installation of a steel wire rope, the steel wire rope is placed in the outer grooves in a method of cooperating with the outer grooves.