The potato virus Y helper component proteinase (HC-Pro) plays important roles in the transmission of the virus Y by the aphid (Myzus persicae). It will be established a new method for tobacco breeding by transmission mechanism of HC-Pro gene of potato virus Y. The helper component proteinase gene of a potato virus Y isolate from Qingzhou, Shandong Province was cloned by RT-PCR and DNA splicing, and the complete nucleotide sequence of the gene was determined. The results showed that the 1 389 bp gene , encoded a protein of 463 amino acids and shared more than 96% and 92% homology with HC-Pro genes of other PVY strains at the nucleotide and predicted amino acid level, respectively. It is suggested that the HC-Pro should belong to a new isolate of potato virus Y. SDS-PAGE showed that the HC-Pro gene was successfully expressed in E. coli.