Batten plates can play a significant role in reducing the bearing capacity of the entire component and preventing the upward warpage deformation in the opening section. The specific number of batten plates should be calculated for the open cold-formed thin-walled steel structure. By theoretical analysis, this study develops the flexural-torsional buckling formula for the open hat-section cold-formed thin-walled axially compressed members with batten plates. The calculating results show that, according to the configuration rule with 40 iy space between batten plates along the opening direction in the open thin-walled steel members, the warpage deformation will be effectively prevented in the opening direction. Besides, the bearing capacity of the entire member will be increased. The proposed calculation methods can actively complement the existing code.