Abstract: In order to solve the control problems of open-off cut composite roof, such as rapid damage, long duration and severe deformation, the structural characteristics of composite roof are obtained through field measurement, and the displacement changes and plastic zone development characteristics of open-off cut floor and side under different iterations are statistically analyzed by FLAC3D software, which reveals that the law of development and deformation characteristics of the plastic and plastic zone of the surrounding rock changes under the condition of single roof and composite roof. At the same time, based on Goodman’s elastic sandwich theory, the mechanical model of composite roof elastic sandwich composite beam is established, and the calculation formula of the limit span of composite roof is obtained. Finally, the parameters of “bolt cable + single pillar” combined support are optimized. The field practice results show that, on the basis of mastering the structural characteristics and failure characteristics of the large-span composite roof, in the support scheme with “strong anchor cable + single pillar” as the core, the average value of 0-4.0 m rock separation layer is 108 mm, and the support scheme effectively controls the deformation of the surrounding rock in the opening of the large-span composite roof.