Since the ancient Greek philosopher Socrates proposed the idea of “acknowledging yourself”, psychologists have never stopped contemplating human nature. The debate over human nature has spawned different psychological counseling theory and counseling techniques, and the painting psychotherapy that incorporates various techniques has received support from various psycho-counseling schools such as psychoanalysis school and humanist school. This article attempt to show the case of House-Tree-Person painting technique and decipher the principle of the art-therapy effect based on psychoanalysis theory, humanism theory, and cerebral hemisphere functional zoning theory.