The relevance of the problem how to form the high school students' professional competences is due to the fact that professionals with "competencies", which have versatile abilities confirmed by practical experience of independent socio -professional problems are demanded. The results of the study indicate that didactic tasks become the most effective resources in this process, which transform the learning goals of the teacher into a productive construct for key professional competences developing in learning and professional activity. In this regard, this article is focused on the scientific and methodological justification of instructional tasks' basic components' structure and content aimed at the development of university students' key professional competencies. The leading method to study this problem is monitoring of students' key professional competencies' formation in the process of didactic tasks' realization. The article presents the theoretical and methodological bases of students' key professional competencies' formation in educational tasks systematic using as a set of knowledge, skills, qualities, experience, and operationally practical ways of activities necessary for professionally -oriented functions' creative performing. The article can be useful to high school teachers, young scientists, graduate students, university Methodists, the students of the teachers' advanced training and retraining system.