Objective To determine if the JX143 strain of the porcine reproductive and respiratory syndrome virus (PRRSV) is the etiological agent of the "Porcine High Fever Syndrome" outbreak in China. We also sought to test the genetic stability of the eDNA clone and to On insight into the structure and function of the PRRSV genome and the mechanism of it's pathology, which will ultimately provide a is for vaccine development using genetic technologies. Methods Specific primers were designed according to the PRRSV genome. The five cDNA fragments covering the PRRSV genome were amplified and cloned into pBlueScript ⅡSK ( + ) vector. A T7 promoter was introduced immediately upstream of the 5'-end.A molecular marker, Mlu I restriction enzyme site, was introduced in the ORFS coding region. This process resulted in the successful construction of two infectious clones. Results Full-length genomic clones of PRRSV were rescued successfully after transfection into MA104 cells. We then compared the growth properties of the rescued virus and the parental virus using a multi-step growth curve. Animal experiments were executed by inoculating the rescued vines into pigs. All results indicated that there was no difference between the parental and rescued viruses in either their virological and biological properties. Conclusion From this study, we concluded that the etiological agent of the "Porcine High Fever Syndrome" outbreak in China is, in fact, a PRRSV, such as the JX143 strain. This is the first report showing a high virulence virus infectious clone of PRRSV in China.