In the past 20 years, the molecular biology take place revolutionized change. The genomics came with the tide of fashion through the automation of computer and the breakthrough of biological information technology. It provides comprehensive research way to understand cancer. We can understand complex process in carcinogenesis, and farther to have chance to develop new therapeutical method. But genomics has its limitation after all. The function of cell is carried out by protein in fact---not by DNA or RNA. And many protein carry modifiable process out not in the nucleic acid or amino acid sequence stage. Modifiable process include different RNA splicing and modification of phosphorylation and glycosylation after translation. From the viewpoint of biomedicine, the protein is the end product of gene expression process and the drug therapy and the diagnosis also frequently take the protein product as a goal. We can analyze different protein expression pattern from normal cell and cancer cell or compare the change before and after drug therapy in cancer cell. These are most application modes in proteomics in present stage. The key point in proteomics lies in understanding the function of protein in vivo. For example, if we can find out the protein which express differently between cancer cell and normal cell, we can use this protein as a marker to trace tumor occurrence. In addition, when developing the drugs, we can screen the drugs which have the actual curative effect through qualitative and quantitative determination of certain protein.。，