Abstract: In this study, the complete sequence of the replicase polyproteinencoding ORF1 of TGEV SC-Y strain was obtained by RT-PCR, the entire nucleotide sequence was determined(GenBank Accession No. DQ390461).Results showed that there were two partially over lapping open reading frames in replicase polyprotein-encoding ORF1 of SC-Y strain , the ORF1a contains 12 053 nucleotides encoding a polypeptide of 4 018 amino acids, the ORF1b contains 8 036 nucleotides encoding 2 678 amino acids. The sequences were compared among different TGEV strains and other coronary viruses. The results showed that the SC-Y has the highest homology with PUR46MAD strain,the ORF1a and ORF1b nucleotide sequences had 995% and 998%, amino acid sequences had 99.2% and 99.8% respectively. The ORF1b is highly conserved among the different coronaviruses.