Abstract: The fast developing technology of bioinformatics has provided a new efficient tool for modern medicine. In particular, since the accomplishment of the human genome project we can now try to understand the phenomenon of life from the point of view of genes, especially with regard to the mechanism of major diseases. Since a biological feature generally involves many genes, DNA microarray chips have been developed to detect the expression levels of thousands of genes simultaneously, the so-called microarray data or large scale expression profile. With these data we can analyze the diseases, and even find new biological features or orderly patterns. Moreover, according to these microarray data we can select the informative genes of a certain disease and construct a classifier or diagonal system for it, which will certainly promote the development of medicine. Furthermore, microarray data have been applied to the analysis of regulation and control among genes, which will be significant for the pathology and treatment of diseases.