According to the modern medical treatment theory, the effect of medical treatment more and more depends on patient's frame of mind. So in design of Bio-clean operation department, the principle of environmental psychology should be taken into account, so as to form a humanistic interior space, which could ease patients' tension and make the operation easy. In this paper, the importance of psychological environment in Bio-clean operation department design is discussed and an advice for the creation of humanistic interior space in three aspects is brought forward.