Phosphorus plays a crucial role in life chemistry. Many phosphoryl proteins and phosphoryl peptides have important biological activities. In the present dissertation, the activities and the mechanism of six N-phosphoryl peptide derivatives which inhibit K562 cells' proliferation and induce K562 cells'apoptosis have been investigated.N-phosphoryl peptide derivatives DIPP-AA_1-AA_2-R were synthesized by using the method previously developed in our lab through coupling reaction of various N-phosphoryl branched peptides and trimethoxyaniline. MTT assay showed that DIPP-Val-Phe-R could significantly inhibit the proliferation of K562 cells represented by the corresponding IC_(50) value at 9.7μmol·L~(-1)The morphological and biochemical properties of K562 cells after being treated with DIPP-Val-Phe-R were characterized, including the nuclear examination by Hoechst 33258 staining, the cell cycle analysis by flow cytometer and the member phosphatidyl serine distribution by Annexin V-FITC probe. The results of the above tests strongly supported the conclution that the tumor cells experienced apoptosis after being treated by DIPP-Val-Phe-R.DIPP-Val-Phe-R was known to induce apoptosis of K562 cell. Studies on the molecular and cellular mechanism involved in this process showed that the apoptosis induced by DIPP-Val-Phe-R was associated with the sustained loss of mitochondrial transmembrane potential (MMP), and the decrease of reactive oxygen species (ROS) and the cytosolic accumulation of cytochrome c (Cyto c). Flow cytometry analysis indicates that DIPP-Val-Phe-R induced the upregulation of pro-apoptotic Bax and the downregulation of anti-apoptotic Bcl-2 and Bcl-xL. Further study showed that DIPP-Val-Phe-R cause the activation of caspase-9 and -3. All the results suggest that DIPP-Val-Phe-R induce the apoptosis through a mitochondria-dependent pathway in K562 cells. Both the regulation of Bcl-2  family members  and  the  mitochondrial   dysfunction  contribute  directly  to  thepro-apoptotic effects of DIPP-Val-Phe-R.