The reflector system of the five-hundred-meter aperture spherical radio telescope (FAST) is designed as rigid panels supported by a flexible cable-net structure. Shape-changing operation in process of observation will lead to relative displacements between the adjacent nodes of the cable-net. Meanwhile,three nodes on a rigid panel are fixed relatively. Thus,adaptive connecting mechanisms between panels and the cable-net are certainly needed to avoid the influence of additional stress during shape-changing operation. The present work focuses on the following aspects according to the technical requirements of FAST. The degrees of freedom and the structure of the adaptive connecting mechanisms are designed,and the finite element model of the reflector system with the adaptive connecting mechanisms is established. Then the theoretical algorithm is applied to verify the results calculated by the finite element analysis. The finite element analysis is carried out to calculate the scope of motion of adaptive connecting mechanisms during the shape-changing of the cable-net,thus providing input parameters for the design of adaptive connecting mechanisms.