Theory of Mind (ToM) refers to understanding and recognition of the person itself and others’ mind estate (such as desire, belief, intention, motivation and feeling, etc.), based on which causative prediction and explanation are made towards corresponding behaviors. So far the correlative researches domestic and overseas of ToM have mainly focused on the normal children; the ability of autistic children’s “theory of mind” which in turn could prove some basic hypotheses of ToM was seldom investigated. We tested “theory of mind” by the modified non-verbal false belief test, the unexpected-content task, based on the former design, then got four results of the study as followed, 1) The non-verbal false belief tasks, more exactly the modified unexpected-content task is suitable to the autistic and mental retarded children; 2)The theory of mind of the autistic children including the low language function ones are significantly lower than that of the mental retarded children; 3)The results of the theory of mind of the mental retarded children is the same with those reported in former researches; 4) Compared with mental retarded children, the autistic children seems to show much difficulties in focusing on the transfer and exchange of article.