The spherical cable network structure of the FAST project of the National Astronomical Observatory is composed of 2225 nodes,6670 main cables and 2225 lower cables. After the installation of the structure, the cable force of the cable network needs to be adjusted to meet the design requirements of the structure. The spherical cable network of FAST Project is connected with the ring beam through 150 edge main cables, the edge main cable adopts the cable structure with adjustable length, and the other main cables are the non-adjustable cable structure with fixed length. The cable network nodes are connected to the ground anchor through 2225 lower cable. The geometric position of the cable network is realized by the adjustment of the edge cable, and the late change of the node of the cable network is realized by the adjustment of the lower cable. This paper introduces the construction technology of the main cable force adjustment of the edge of FAST spherical cable network structure.