Abstract: The Out-drum Cement Solidification process is taken as the case of study in this paper, the process flow of the Out-drum Cement Solidification of radioactive liquid was introduced, the fundamental requirements of the Out-drum Cement Solidification process line were proposed. According to the fundamental requirements, relevant equipment of the Cement Solidification process line was set up, and the layout of the Cement Solidification process line was carried out based on the design principles of non-standard box room. The working process of Cement Solidification process line was explained, and the necessary support systems for the Cement Solidification process line were proposed. In response to the problems of the poor cleaning effect of the Out-drum mixer, the poor dredging effect of the dry powder feeding pipe, and difficult maintenance of some equipment outside the hot cell, the scheme demonstration was conducted through engineering prototype testing. Finally, a design scheme for the Out-drum Cement Solidification process line of radioactive waste was formed, providing a reference for the design of other Cement Solidification process lines.