Nine new N 12 -ethyl substituted indolocarbazole derivatives were synthesized. Their structures were identified by 1 H NMR, 13 C NMR and HRESIMS. The thiazolyl blue tetrazolium bromide (MTT) method was used to evaluate the cytotoxicities of these derivatives against A549, HepG-2 and Hela cell lines, while the cell counting kit-8 (CCK-8) method was used to evaluate cytotoxicity against K562 cell lines. The results showed that compounds 7～9 displayed comparable cytotoxicity to adriamycin (