We present a frame-based software requirements specification language (FSRSL) and its environment, a knowledge-based rapid prototyping system (KBRPS). KBRPS applies a combination of rapid prototyping, operational specifications, and transformational implementation methodologies as an integrated software paradigm. FSRSL uses frame representation for object-oriented modeling. Data, process, control, and assertion are four types of modeling primitives in FSRSL. Based on these modeling primitives, it is easy to describe and compre hend real world problems. FSRSL has improved specification language techniques on naturalness of software construction, inheritance properties, reusable specifications, and database applications. Specifications written in FSRSL can be executed as a software prototype, and the finalized FSRSLspecifications can be transformed directly into program codes as software products. KBRPS supports FSRSL to develop software efficiently based on the integrated paradigm. The KBRPS system contains a graphic representation of a conceptual model for modeling system structures, a FSRSL language for describing the textual form of the conceptual model and for specifying detailed system behavior, a database for storing specification files, and a knowledge base for storing rules of software development. A real problem is given to illustrate the application of FSRSL.