This study aimed to determine problems of preservice teachers on technological pedagogical knowledge skills. The socio-economic transformations taking place in the country indicate the presence of a society's need for a person who has the ability to set goals and achieve them independently. In this regard, education is faced with the task of forming the personality of the future teacher as a subject capable of diagnosing the process and results of its activities. However, the educational technologies used at the university most often alienate students from educational activities, offering ready-made goals, ways to solve them, and thereby exclude them from the diagnostic process. A change in the modern educational situation actualizes the formation problem of technological pedagogical knowledge skills in a future teacher. The article deals with the development of a scientifically-based system for preparing students for diagnostic activity, which includes theoretical and practical training at the university. The practical significance of the research results lies in the possibility of using the developed methodological recommendations in the practice of training specialists in the field of primary education.