Abstract: The cell nuclear DNA contents in the root tip of several species of Liliaceae were measured by the Feulgen microspectrophotometry. The genome size of each species was calculated according to their nuclear types.They were as follows:A. cepa L.18. 16× 10⁹ bp,A. chinese G. Don. 12. 84 ×10 bp,A.ascalonicum L. 10. 44 ×10 bp and H. citrina B. 7. 8 ×10 bp.The results suggested that the genome size should be more suitable to be used as a characteristic index of biological research than the nuclear DNAcontents, because the genome contained all genes which maintain the organisms' survival and refelected the entire specific genetic informations. This study will provide valuable reference not only to Cytology,Taxonomy and Genetics,but also to Molecular biology.