Objective To investigate the population dynamics of blood-sucking insects and detect the pathogen of rodents in Xisha Islands of China, so as to provide information for prevention and control of infectious diseases in the area. Methods From January to July in 2014, we collected blood-sucking insects in Yongxing and Shi Islands twice a month using light traps. The specimens were identified by morphologic characters and molecular markers. Meanwhile, the population size was calculated. The pathogenic infections of rodents were detected by immuno-colloidal gold chromatographic test strips and PCR assay. And the ectoparasites in the rodents were initially identified by morphologic characters. Results The dominant species of blood-sucking insects in Xisha Islands were species of Genus Culex, Armigeres and Culicoides, and in April the population density of biting midge was the highest (55.55%, 6 984/12 573). Phlebotomine sandfly specimen was also collected and identified as Sergentomyia baily (n=11) by mtDNA-COⅠ sequences. The positive rates of Staphylococcus aureus enterotoxin type A and Botulinum toxin type A were 3.45% (1/29) and 14.00% (7/50) in the rodent serum samples, while all the samples were negative for Tsutsugamushi disease and Plague antibodies. Sta58 gene of Rickettsia tsutsugamushi was amplified by nested PCR in 70 rodent's spleen tissues, with the positive rate being 11.43% (8/70). A total of 248 ectoparasites were collected, and 93.55% (232/248) of them was gamasid mites. Conclusion The population dynamics of blood-sucking insects has no obvious change. Phlebotomine sandflies has been first recorded in Xisha Islands. The infection rates by Rickettsia tsutsugamushi and two bacterial toxins are high.