The model of the knowledge society development requires from a modern educator a wide range of skills and competences to successfully fulfill his professional functions. The formal and non-formal education system’s aim is a qualitative scientific-methodological support of a specialist, as well as realization of content and technologies of professional development in variable educational models. The article presents the theoretical principles and the analysis of modern educational variable models of educators’ professional development in the system of formal and non-formal education, conducted under the research “Professional Development of Specialists in the Adult Education System: History, Theory and Technologies” (2017-2019). In particular, there are systematized the research concepts; the initial monitoring is prepared and conducted in order to identify the problems and difficulties in the process of specialists’ professional development, in quality of scientific-methodological support, in ascertaining the reasons of problems’ appearance; it is carried out a complex study of psychological-pedagogical factors under which the specialists’ professional development in the formal and non-formal education models is made more effectively; the content and technologies of educators’ professional development in the education system for adults is theoretically grounded and experimentally verified. The author developed, experimentally verified, and tested the scientific-methodological support of educators’ continuous professional development in the course and intercourse training; the quantitative and qualitative analysis of the experiment’s results is made, the pedagogical interpretation of the obtained experimental data is suggested; there are outlined the perspective tasks of specialists’ further professional development in the system of formal and non-formal education. It is expressed that if the education system for adults is provided with the up-to-date variable educational models in the system of formal and non-formal education, then it is possible to increase the professional development of the teaching and scientific staff to make them easily oriented in the constantly changing socio-economical conditions, professionally realized in the knowledge society, carry out professional self-actualization, and strive to develop their professional self-awareness.