Abstract: The subject of the research is the phenomenon of extremism. The need-functional model of the psychosemantics of extremism is based on the procedural and instrumental model of extremism. The structure of the procedural and instrumental model of extremism is being described with the help of such categories as 'assessment', 'force', 'activity', 'tolerance', 'trueness', 'identity', 'aggression' and 'rate' of social transformations. The theoretical model of extremism psychosemantics consists of the following categories: assessment of social justice (central category), the rate of social transformations, social activity, social force and social energy as well as the degree of influence of social forces. The method of theoretical triangulation combines opportunities of several scientific approaches and allows to explain and interpret complex facts, phenomena and processes. In fact, triangulation means determination of the location of the third point when the other two points are known. The authors of the article have used this method to create the need-functional model of extremism psychosemantics. Thus, the results of the theoretical triangulation allow to substantiate the following initial theoretical provisions which combination describes the essence of the need-functional model of extremism psychosemantics offered by the authors. The social and psychological peculiarities of the phenomenon of extremism are consistuted by the verbal or active representations of justice demonstrated during social interaction between actors (individuals, groups, communities or states). These include justice viewed as a) the distribution of social goods, values, social roles and statuses and b) priority of a particular religion, life style, behavior or relationship. According to the authors, extremism is based on the eternal need of human and society in justice. Consequently, the function of extremism is to try to satisfy these needs by using subjective standards of social justice. Taking into account the psychosemantic nature of the phenomenon fo extremism, we should fight against extremism by developing socially acceptable representations of justice and ways of achieving it.