Abstract: Objective To investigation natural focus of spotted fever in Chengmai county, Hainan Province. Methods Rickettsia cultrue from probable patients' blood and mouse' blood samples by modern Shell vial Methods were performed and identification of isolates were conducted by PCR amplifying and sequencing of 16S rRNA, gltA, ompA, 17 kD and groEL genes. Specific IgG antibody against the emerging spotted fever group rickettsiae was detected on 812 serums from healthy farmer population collected from 10 villages in Chengmai county, 18 dogs, and 44 mice by IFA. Rickettsiae groEL genes were directly amplified and sequenced on patients' blood, mouse blood and dog blood DNAs and vectors including ticks, mites and fleas. Results A total of 11 isolates of novel spotted group rickettsiae from patients and 7 isolates from Rattus fulvescens were isolated. Genetic analysis showed that these isolates were closely related to R.heilongjiangensis genetically However,isolate have different phentype based on the assasy. The sequences of 16S rRNA, gltA, ompA, groEL and 17 kD genes demonstrated all isolates were the same epidemiological clone. The evidences of amplifying and sequencing of groEL genes from patients, mouse and dogs blood DNA and vectors including ticks, mites and fleas demonstrated 100% homologies with that of the isolates from the patients and mice. The prevalence of IgG antibody against the epidemiological spotted fever group rickettsia for control adult population, domestic dogs and mice were 46.1%,88.9% and 11.4% respectively. Doxycycline was effective for curing probable patients experimentally. Conclusion An emerging spotted fever is prevalence in Chenmai county, Hainan province. Diagnose and differential diagnose between spotted fever and others febrile diseases should be emphasized in clinics. Killing ticks in farmer's houses and bodies of domestic animals and prevention from tike biting should be propagated in the endemic areas. Further investigation of other tickborn rickettsiosis should be performed.