Abstract: Objective:The aim of our study was to identify the in vitro antitumor activity of two novel Platinum (II) com -plexes against SW620 cell line, describe the effect of the two drugs on cell apoptosis, and compare the depressant effects of the two new drugs with those of oxaliplatin. Methods:The human colon carcinoma cell line SW620 was used as the re-search object. Three antitumor agents, oxaliplatin, pyrazine and pyridine, of different concentrations, were administered to the SW 620 cell line at logarithmic growth phase for 24and 48hours, respectively. The colony inhibition ratio was then de-termined using human tumor cloning assay (soft-agarose colony formation test). Cell apoptosis was assayed by means of Annexin V-FITC binding assay. Changes in morphology and ultra-structure after administration of the three drugs were ob-served by scanning electron microscopy. Results: In human tumor cloning assay, after the SW620 cells were treated with oxaliplatin, pyrazine and pyridine for24hours, the half inhibiting concentration (IC 50) was 266 .51, 176 .18and 159 .25μ mol/L, respectively. And 48hours after the administration of the three drugs, the IC50was 158 .84, 161 .27and 125 .67μ mol /L, re-spectively. The strength of drug action, from high to low, was pyridine, pyrazine and then oxaliplatin, with significant differ-ences among the three ( P<0.01). In the Annexin V-FITC binding assay, our data indicated that all of these drugs can induce apoptosis of the cell line SW 620 , with concentration and time dependence in the drug action. Cell death increased as the concentration augmented and the time of drug action extended. The order for the intensity of drug action can be listed from high to low as follows: pyridine, pyrazine and oxaliplatin, with significant differences among the three (P<0.01). By scanning electron microscopy, typical morphological changes of apoptosis were observed. Conclusion : Based on the results of this study, we conclude that the two new type platinum (Ⅱ) complexes have demonstrated a satisfactory in vitro anti-tumorous effect on the colon cancer cell line SW 620 . The drug action of the chemotherapeutic agents presents concentration and time dependency and the efficacy of the drugs are higher compared to oxaliplatin. Finally, we conclude that one of the targets in the drug action is induction of cell apoptosis.