Abstract: A series of 5-amino-2-(benzylthio)thiazole-4-carboxamide derivatives were designed and synthesized to discover novel compounds with anti-tumor activity. Compounds DDO-5401 - DDO-5416 were synthesized using 2-amino-2-cyanoacetamide as the start material. The structures of the synthesized compounds were confirmed by IR, ¹H NMR and ESI-MS. The in vitro anti-tumor activities of the synthesized compounds were determined by MTT assay in HCT116, HepG2, A549, MDA-MB-231 and MCF-7 cell lines. Target compounds showed good anti-tumor activity especially in A549 cell line. SAR study showed that electron donating groups were more favorable than electron absorption ones. Compound DDO-5413 exhibited noteworthy activity in MDA-MB-231 and MCF-7 cell lines with IC₅₀ value lower than the positive reference dasatinib. It suggested that DDO-5413 might be the candidate for further investigation.