For the purpose of advancing our research on diverse C-20 decorated derivatives of camptothecin (CPT), 46 new CPT acylthiourea derivatives were synthesized and evaluated in vitro for their cytotoxicity. All the compounds showed promising in vitro cytotoxicity against six tumor cell lines (Hep3B, MCF7, A549, MDA-MB-231, KB and KB-vin). Out of them, compound c20 possesses remarkable in vitro cytotoxic activity and is more potent than topotecan. Mechanistically, c20 not only induces cell cycle arrest and cell apoptosis in A549 cells, but also inhibits Topo I activity in the cell and cell-free system in a manner similar to that of topotecan. In both xenograft and primary HCC mouse models, c20 displays significant in vivo anti-cancer activity and is more potent than topotecan. In addition, the acute toxicity assay showed that c20 has no apparent toxicity to mouse liver, kidney and hemopoietic system of the FVB/N mice. Take together, these results indicated that compound c20 could be a potential anti-cancer candidate for further clinical trial.