Existential psychology, with its roots in existentialist philosophy, has developed in concert with humanistic psychology to confront psychoanalysis and behaviorism. The theoretical perspectives within existential psychology are constantly in dispute and contradict each other. In this paper, we explore the representatives and characteristics of the four theories of existential psychology: existential analysis (Switzerland), meaning therapy (Austria), existential humanistic psychology (USA), and the British school, based on the chronological development of existential psychology, with the aim of gaining a deeper understanding of the existential psychology system.