Modular design and construction technology are one of the most important features of the 3rd-generation nuclear power plant, and the opening-top construction is the precondition of application of modular technology. Combined with the powerhouse structure and construction characteristics of nuclear power plant project, this paper proposed four kinds of floor structure schemes for opening-top construction, and summarized these floor structure schemes structure characteristics, design points, scope of application, advantage and disadvantage. Finally, the technology conditions of opening-top construction were suggested, which could provide references for the application of opening-top construction technology in nuclear power project.