The invention discloses a closed steel bar framework of a thick-roof arch structure and an optimization method. The closed steel bar framework comprises a roof steel bar framework positioned on a roofof the arch structure, partition steel bar frameworks connected to two end parts of the roof steel bar framework, and bottom plate steel bar frameworks connected to the bottoms of the two partition steel bar frameworks, wherein the top plate steel bar frames are arranged in a layered mode, and the interlayer steel bar meshes are connected through top plate single-limb stirrups and are connected to a group of steel bar supports. The method mainly adopts the methods of upright post bearing, single-limb stirrup replacement and the like during the steel bar optimization. According to the closed steel bar framework of the thick-roof arch structure and the optimization method, the roof steel bar frameworks are arranged in the layered mode, so that the layered pouring, vibrating and stress of the roof are conveniently carried out; vertical steel bar frameworks and cross beams among the steel bar frameworks are arranged, so that the force bearing performance of roof structure after pouring isimproved; according to the equal strength method and the equal area method, closed stirrups are replaced by the single-limb stirrups, so that the stress of the top plate structure is ensured, the steel bar using amount of the whole arch-shaped structure closed steel bar framework is further optimized, and the construction is convenient, and the working efficiency is improved.