Abstract：【Objects】To isolate and identify the pathogen of the large outbreak of dengue in Guangdong province in 2014. To understand the origin and the phylogenetic characteristics of the isolates，and provide scientific foundation for the surveillance and prevention of dengue fever.【Methods】Collected the patient serum samples over all the Guangdong province during the 2014 outbreakand sequenced all the products. Then the Phylogenetic，Bayesian phylogeography and mutations analysis were carried.【Results】40 DENV-1 strains were isolated and identified. 40 complete E gene sequences and 6 complete genome sequences of DENV-1 were obtained. Phylogenetic analysis with E gene sequences revealed that the 40 isolates were classified into two genotypes including 16 genotypeⅠ（Asia）and 24 genotypeⅤ（America/Africa）. 14 genotypeⅠisolates were clustered closest with isolates from Guangdong province（2013）and Sigapore（2013）which share the nucletide identities of 99.6% ~ 99.9%，other two genotypeⅠisolates were clustered with strains from Malaysia（2013） and both share the nucletide identities of 99.7% ；24 genotype Ⅴ isolates were all classified in one clade with striains from Bangladesh（2009），China（2009）and Bhutan（2013）which share nucletide identities of 99.0%-99.9%. Further analysis with six complete genome sequences showed that five isolates were clustered closest with strains isolated from Guangdong province（2013）share the nucletide identities of 99.6%-99.8% while the sixth stains closest with strains isolated from Myanmar（2002）share the nucletide identities of 98.8%. The isolates have five amino acid mutations compared with strains epidemic in Guangdong province in 2013，three mutations（S88V，E203G，T275R）are in the EⅡ domain and one mutation （S305P）is in the EⅢ domain which associated with virulence.【Conclusions】During the outbreak in Guangdong province in 2014， DENV-1 is the predominant causative serotype，and there are at least two different kinds of genotypes of DENV-1 largely epidemiced in the whole province. Evolution analysis reveals the multiple origins of the isolates which may origin from Guangdong province， Sigapore，Malaysia，Myanmar so that we should enhance the study and surveillance of autochthonous and vectors in order to understand the epidemic way of dengue in Guangdong province. The isolates have had four mutations in the domain associated with virulence which remain further study to know their biological effects.