Abstract: This article is dedicated to the biographical path of the prominent Russian and Soviet legal scholar and social psychologist M. A. Reisner and his contribution to Leon Petrazycki’s psychological theory of law. Biography of the scholar is viewed in the context of his socio-philosophical pursuits and transformation of his outlook. The main attention is given to the synthesis of Marxist and psychological theory of law, as it became the key area for M. A. Reisner’s scientific pursuits. The study refers to the comparative aspect, draw parallels between the theories of L. Petrazycki and M. A. Reisner, indicating their similarities and inconsistencies. The basic research method lies in the analysis of the scholar’s doctrinal contribution to the psychological theory of law, examination of his autobiography and works of other researchers, who left valuable reminiscences about M. A. Reisner. The scholar scrupulously worked at the development of the concept of intuitive law and its transformation into the positive law, as well as substantiation of the proletariat's right to revolution. However, some of his conclusions cause reasonable doubt. Particularly, in the context of modern legal consciousness, the subject of law is an individual rather than a social community (class), which M. A. Reisner believed was fair. The author emphasizes Reisner’s great contribution into the study of socio-psychological basis of law. Despite a certain idealism of his works, the scientific contribution of M. A. Reisner manifests as the brightest layer of the national science on law, which was and remains of great relevance due to lack of research conducted on its multiple aspects.