The dengue viruses (DEN, genus Flavivirus, family Flaviviridae) are mosquito borne and have caused 100 million cases of dengue fever each year in most tropical and subtropical areas of the world. However, in the southwest area of Yunnan-Guizhou Plateau, China, the previous work demonstrated that different geographic strains of Aedes albopictus were susceptible to dengue virus. In this study, we collected 456 sera samples from patients with fever and 994 sera samples from healthy population in Dushan and Xingyi area of Yunnan-Guizhou Plateau, China. All sera samples were tested for dengue IgG by enzyme-linked immunosorbent assay (ELISA). Patients' sera samples were tested for dengue IgM and DEN antigen was checked in the sera of 6 from 456 samples with which C6/36 cell inoculated by IFA. The results indicate that these patients with fever were infected with DEN-2 and suggest that DEN infection had existed in Dushan and Xingyi area of Yunnan-Guizhou Plateau, China.