Abstract: The five hundred-meter Aperture Spherical Radio Telescope (FAST) is supported by a cable-net structure, whose form changing operations would lead to about 500MPa of stress range. This stress range is more than twice that defined by the codes regarding cable-net structures. Thus, the cable-net structure is the most critical and fragile part of the FAST reflector system. Therefore, the present paper mainly focuses on the following two aspects. 1) Based on the estimated tracking trajectory of this telescope during its service life, finite element methods were used to clarify the fatigue resistance requirements for the cables used in this telescope. 2) A new type of steel cable system was developed, one with fatigue resistance and durability capable of meeting that requirement.