In ancient Chinese academic criticism, the terms"xu"(insubstantial) and"shi(substantial)were used as evaluative terms. However, distinguishing what was" xu and what was"shi was a subjective judgment. In the critical view of the General Catalogue of The Complete library of the Four Treasuries(Siku Quanshu Zongmu, the concept of"xu-shi"was multi-layered, with a dialectical structure between the different layers. In terms of academic content, xu-shi mainly referred to whether the contents had practical application, and whether the nature of the content was related to human affairs Regarding academic methods, the concept primarily referred to reliability. Since contentand methods were two sides of the same coin, if some works are considered"shi"in both regards, they might be called"shi-xue"in the General Catalogue. However, " shi-xue"was considered relatively practical in the General Catalogue, because it placed a higher value on utility. There was another three layer dialectical structure of the General Catalogue " xu-shi"theory in terms of academic practicality. In view of purposiveness, shi-xue"still meant insubstantial without statecraft application. Furthermore with a view to utility, writings without practical effect but only statecraft purpose were considered insubstantial. In terms of practical action, effective suggestions without execution were also considered only"dead letters. Considering the versatile character of xu-shi, and the complexity of the"xu shi"theory in the General Catalogue, specialized recent research on"Shi-xue "is worthy of discussion regarding the validity of its academic conceptualization