Abstract: According to the sequence of RNA polymerase gene of avian leukosis virus subgroup J (ALV-J) strain published in GenBank,two pairs of primers were designed and synthesized.The outer primers amplified a fragment of 478 bp in length, and the inner primers amplification fragment size was 314 bp in length, a nested PCR assay for rapid detection of ALV was established.A specific 314 bp fragment was amplified from RNA templates of ALV strain,but no bands were amplified with templates extracted respectively from avian influenza virus(AIV) subtype H9,Newcastle disease virus(NDV), infectious bursal disease virus(IBDV),egg drop syndrome virus (EDSV), reticuloendotheliosis virus(REV), avian reovirus (ARV), Marek’s disease virus(MDV). Sensitivity of the 1st and 2nd amplifications by the nested PCR assay was 100 pg and 1 fg,respectively.The sensitivity of the 2nd amplifications was increased by 10⁵ times.The results showed that the nested PCR was specific,sensitive,rapid,and accurate,and could be used as a routine assay for the detection of ALV.This method had good reproducibility, specificity and sensitivity, and might detect low content ALV accurately and rapidly. This method could be used as a method for the diagnosis and detection of clinical cases,and for molecular epidemiological investigation of ALV.

Key words: avian endogenous ALV-J; nested-PCR; detection