Species diversity and genetic diversity of crop plants including food crops,cash crops,fruit crops and vegetables etc.and their wild relatives in China were assessed.Concept and category of germplasm resources were defined scientifically and systematically.Theory of hierarchical structure of germplasm resources was also proposed.It was raveled that there exist 9631 species of food and agricultural plants in China with clear distribution,characteristics and/or uses.Profiles of crop germplasm resources in China were basically understood.Totally 528 kinds of crops in China were identified for the first time,including 1339 cultivated species and 1930 species of their wild relatives.Further,the criteria for intra-specific classification based on agronomic characters were optimized.Botanic and biological characteristics and genetic diversity of 987 varieties,978 bio-types and 1223 agronomically-specific types existing in landraces of the crops in China were investigated.It was suggested that China is the center of origin or one of the centers of origin of some special genes including the genes conferring nakedness,glutinousness,dwarfism and sterility etc.in cereals.Six volumes of a monograph titled "Crops and Their Wild Relatives in China" were published and a monograph titled "List of Species of Food and Agricultural Plants in China" was in press,leading to the establishment of the theoretical system of the discipline of crop germplasm resources.The thorough diversity assessment would provide the base to effectively use crop germplasm resources and ensure food security and sustainable agricultural development in China.