In recent years, due to the advantages of high construction efficiency and less environmental pollution, prefabricated housing has been of increasing interest and vigorously promoted. However at present, most prefabricated houses simply pursue an increase in assembly rate, and the floor plan design still continues to follow the traditional design method of housing, which does not meet the requirements of industrialization and cannot achieve the goal of product diversification. This paper puts forward a method for floor plan designs of prefabricated houses whose core is building plane module libraries. The modules in module libraries all conform to standardized and refined designs. A new residential floor plan can be obtained by selecting and recombining modules in module libraries. The richer the module library, the more diverse the results will be under the same combinatorial logic, which can greatly improve design efficiency. In addition, this paper probes the method of creation and applications of plane module libraries in detail, so as to provide a new idea for floor plan designs of prefabricated houses. This research is of great significance for improving the efficiency of floor plan design of prefabricated housing and realizing goals of standardization and diversification of prefabricated housing development.