In the article the questions of automation of designing and development of complex applied informationcomputing systems are considered. The technology of designing applied software systems is briefly described, based on the project approach and the tool complex Project Generator. On the example of concrete application systems, the main provisions of this approach are described. In the Computing Center of the Russian Academy of Sciences, a number of large information systems were developed in different years with the help of the Project Generator. The article lists some of them, their characteristics are given and the efficiency of using the Project Generator technology is shown.