7-[(3-piperidyl)-1-propinyl]-camptothecin (CPT21) is a novel semi-synthetic water-soluble analogue of camptothecin. In this context, we assessed the anti-tumor activity of CPT21 both in vivo and in vitro and explored its molecular mechanism. We found that CPT21 presented a broad anti-tumor spectrum against ten cancer cell lines in vitro, and the IC(50) values ranged from 0.1 to 12.0 microM. CPT21 was also capable to interrupt the DNA topoisemerase I activity and caused DNA double strand breaks during DNA replication. Proportion of apoptotic SGC7901 cells induced by CPT21 showed a time- and concentration-dependent increase accompanied with the decrease in mitochondria membrane potential (DeltaPsim). We also observed that CPT21 up-regulated the protein expression of p53, phospho-p53, p21, BAX, phospho-c-Jun NH2-terminal protein kinase (JNK), meanwhile down-regulating the protein expression of Bcl-2, procaspase-9, XIAP, and phospho-ERK1/2. In the study of SGC7901 xenograft model, the results suggested that both 5.0 mg/kg and 10.0 mg/kg CPT21 achieved high anti-tumor activity, and the tumor inhibition rates were 42.5% and 75.1% respectively. Taken together, our study demonstrates that CPT21 displays an extensive anti-tumor spectrum and CPT21 can induce the apoptosis of SGC7901 cells via activating the caspases cascade followed by disrupting mitochondrion function.