Glaucocalyxin A (GLA) is an active natural tetracyclic diterpenoid isolated from the traditional Chinese herb Isodon glaucocalyx (maxin) Hara. In this work, a series of thiazole type derivatives based on GLA were designed and prepared. Their antiproliferative activities against six tumor cell lines (HepG2, NCI-H460, JEG-3, K562, HL-60 and Hela) were evaluated in-vitro. The results revealed that the introduction of aminothiazole substructures into A-ring of the GLA could improve their antiproliferative effects significantly. Among them, N-alkyl thiazole derivatives showed remarkably activities to the six tumor cell lines. Especially, compounds 6 and 8 presented significant antitumor activities against HL-60 and Hela cell lines with IC50 as low as 0.51 µmol•L -1 , which were better than the positive drug adriamycin. The apoptosis morphology and flow cytometry studies indicated that the thiazole-fused GLA derivatives could induce apoptosis of tumor cells.