The invention discloses an operation method for increasing the operation space in a spacecraft sealed cabin. The method is characterized in that a plurality of equal-height blocks are arranged on thebutt joint face of the spacecraft sealed cabin, parallel long beams are arranged on the equal-height blocks, slidable support platforms are arranged at the tops of the long beams, and an operator canconveniently perform operation on the support platforms. The method has the advantages that the method is simple in equipment mounting and operation, convenient in use, high in safety and the like, the openness in the sealed cabin is increased, the operation space in the sealed cabin is increased greatly, visuality is improved effectively, and when the operation staff enter the sealed cabin to perform operation, the operation staff can use multiple postures such as standing, sitting, lying and groveling to complete final assembly operation in the cabin on the support platforms.