In order to improve the anticancer activity of emodin, seven emodin derivatives containing nitrogen heterocycle and three emodin derivatives containing quaternary ammonium salt were designed and synthesized by suitable modification at C6 position of emodin, their structures were characterized by IR, H-1 NMR and MS and their activities against leukemia cell line Molt-4 and lymphoma cell line CA46 in vitro were tested by MTT method. Thereinto, compounds 8, 9a+9b, 20a, 20b and 20c show higher anticancer activities than emodin, which indicates that benzimidazole and quaternary ammonium salt are good pharmacophores for the anticancer activity of emodin. We propose to introduce many such pharmacophores into emodin to improve the anticancer activity of emodin in further.