MOTIVATION: The rapid growth of DNA sequence data creates a need to find graphic tools to study DNA sequence in a perceivable form. A large number of scholars work hard in this field. However, it is difficult to handle the following problems in one graph: (i) degeneracy, (ii) loss of information, (iii) difficulty of observing in multi-dimensional graph, (iv) difficulty of visualization when representing long DNA sequences and (v) need to reflect useful information. RESULTS: DV-Curve (Dual-Vector Curve) using two vectors to represent one alphabet of DNA sequences not only avoids degeneracy and loss of information, but also has good visualization no matter whether sequences are long, and can reflect the length of DNA sequence. The applications of the DV-Curve on mutation analysis and two types of similarity analysis are presented in detail. DV-Curve is a significative tool by which biologists could find useful biological knowledge. AVAILABILITY: The corresponding software of DV-Curve is available at http://bmchust.3322.org/Data/Soft/332-DV-Curve2.0.zip.