Reticuloendotheliosis virus（REV），a common avian neoplastic virus，could induce immunosuppression in infected chickens and bring huge economic losses to poultry industry in China. In this study，a REV strain was isolated from chicken flocks in a parental farm in Shandong Province through inoculating DF-1 cells and named as SD2101. In order to investigate its genetic evolution characteristics，six pairs of primers were designed and synthesized to obtain the whole genome sequence of its provirus by using PCR amplification，followed by sequence alignment and analysis on genetic evolution with the reference strains downloaded from GenBank. The results showed that the provirus was with a typical genome structure of replication-competent retrovirus，with the highest homology with HA1101 which was isolated from chickens in Jiangsu Province in 2011. It was found that，by analysis on genetic evolution，SD2101 strain was on the same evolutionary clade as most domestic isolates. In order to identify the pathogenicity of SD2101 strain，the isolate was inoculated into one-day-old specific pathogen free（SPF）chickens，which was then evaluated by body weight，indexes of immune organs and immune response of inactivated vaccine. In conclusion，the growth and immune functions of one-day-old SPF chickens were significantly inhibited by SD2101 strain. Compared with the reference strain，a small degree of genomic sequence variation was observed in SD2101 strain，with certain pathogenicity. Scientific data was thus provided for further epidemiological research on REV，as it was suggested to focus on and monitor the virus in practice.