By juxtaposing the cultural unconscious with relevant psychoanalytic concepts by Freud, Jung and Lacan, this article attempts to expound the connotation of the cultural unconscious from the levels of individual, collective and linguistic sign unconscious. Then it proposes a model to discuss the relationship between the cultural unconscious and identity construction, which may provide a new perspective for the theoretical framework of L2 writer's identity construction. Based on the model, the author makes a case study on an American Chinese L2 writer, Ha Jin. Ha Jin's fiction reveals the cultural unconscious manifested in his writing and reveals his psychological mechanism of identity construction in the conflict and integration of Chinese and Western cultures.