The seroprevalence of Kaposi's sarcoma-associated herpesvirus (KSHV) is high in Xinjiang, China. But the seroprevalence of KSHV and risk factors are still unknown in Gansu which is adjacent to Xinjiang.Six hundred and seventy-eightserum samples of the general population and 87 serum samples of syphilis patients from Jiuquan, Gansu were tested for antibodies against KSHV, including one latent protein (ORF73) and two lytic proteins (ORF65 and K8.1) using the ELISA. The total KSHV-seropositive rate was 15.9% in 678 serum samples in the Jiuquan area, and the KSHV-seropositive rate of males was higher than females (18.0% vs. 14.6%, p > 0.05). The Uygur, Kazakh, Hui, Manchu, and Mongolian populations had a higher seroprevalence of KSHV than the Han population (43.8%, 40.0%, 34.5%, 30.3%, 35.0% vs. 11.0%, respectively) among the ethnic groups in Jiuquan. Compared to the Han, Uygur, Kazak, Hui, Manchu, and Mongolian people had an increase in the risk of KSHV of 528.9%, 439.1%, 325.6%, 251.6%, and 335.4% (p < 0.001, p < 0.001, p < 0.001, p = 0.002, p = 0.003, respectively). The serum prevalence of KSHV in subjects aged < 20 years, 20-50 years, and >50 years was 13.8%, 14.7%, and 20.1%, respectively. Compared to the subjects aged < 20 years, 20-50 years and >50 years had an increase in the risk of KSHV of 7.4% and 56.9% (p = 0.829 and p = 0.204, respectively). Compared to the positive rate of KSHV in the general population of Anhui, the positive rate of KSHV was significantly higher in the general population of the Jiuquan area (15.9% vs. 9%, p < 0.01). There was no significant difference in the positive rate of KSHV between the Han population of Jiuquan and the Han population of Anhui (p > 0.05). In the population of syphilis patients in the Jiuquan area, the positive rate of KSHV was 30.7%, which was higher than that of the general population in the Gansu area (p < 0.05). This study indicates that Gansu has a high seroprevalence of KSHV. Ethnicity and syphilis are risk factors for KSHV infection.