According to concept of dinucleotide, this paper proposes a graphical representation of dinucleotide. In this way, the graphical representation can not only show sequence one-to-one, but also can be easily converted into the original sequence. Then this paper extracts cross- correlation function to characterize the degree of similarity from representation of dinucleotide. After applying our approach to nine kinds of viruses, it can be found that our conclusion is almost consistent with the reported data. After the analysis with the method of inter-class, it can be found that our data can classify different viruses well. Our approach can more easily extract data and distinguish the different classes than previous results.