In his book Beyond the Principle of Music, he put forward the instinct of life and the instinct of death, and thought that there was a more universal principle in people's hearts than the principle of music. The principle of forced repetition is the instinct of death, the instinct of death is the instinct of destruction, and the instinct of life is the instinct of love. In ego and id, the theory of personality is put forward, that is, personality consists of ego, id and superego.

It is difficult to understand Freud's works without the basis of psychoanalysis. It is suggested to start with the introduction of books, and then read Freud's Introduction to Psychoanalysis, which is equivalent to Freud's own Introduction to Psychoanalysis.

There are also Psychology of Love, Interpretation of Dreams, Research on Hysteria, Pathology of Daily Life, Three Treatises on Sexology, Outline of Psychoanalysis, Self and Collective Psychoanalysis, Civilization and Dissatisfaction, Da Vinci and a Childhood Memory, and so on.