The article describes the algorithm of the predesign researches and modeling of information systems. The implementation of the algorithm is required to solve the relevant scientific problem of increasing the effectiveness of pre-work for development of information and technical systems. The list of basic procedures is required for the pre-work for the stage of conceptual design of information systems. This method will improve the efficiency of modeling process, and pre-work for creation of information systems through the implementation of a systematic approach for analyzing and synthesizing it.