Abstract The plastering machine can effectively improve the plastering efficiency, and the plastering process mainly includes filling the mortar, plastering, floating mortar, and compacting mortar. All of these function is completed by a plastering device. The diversity and complexity of the device increase the production cost and the weight of the whole machine. In order to guarantee the plastering quality and optimize the institution, this thesis designs a plastering device that integrates mortar supply, plastering, surface flattening, and compacting functions. The working process of the plastering mechanism includes upward plastering and downward flattening, mainly achieved by the rotation motion of the hopper. The contour shape of the hopper was designed using the principle of cam mechanism, and the upward plastering and self-locking of the hopper after reaching the top were designed using the principle of connecting rod mechanism. The hopper is supported by two pneumatic springs. The flipping force of the pneumatic springs during the upward plastering and downward plastering processes was analyzed and calculated, which provides the basis for choosing the power of the driving motor.