Abstract: 【OBJECTIVE】To clone the site A of S gene of transmissible gastroenteritis virus and to construct the prokaryotic expression vectors of site A.【METHOD】The target gene of the site A of S gene was amplified respectively by RT-PCR with a pair of primers, which was designed according to the published sequence of TGEV S gene with primer 6.0 software. The amplified gene was cloned into the vector peasy-T , Then the gene and the vector PET-32a（+）was digested by EcoR I and Xhol I. The recycled genes were inserted into the multiple cloning sites of the vector PET-32a（+），The recombinant plasmid was transformed into BL21(DE3) strain and the positive plasmid was identified by restriction enzyme, PCR and sequencing.【RESULTS】The results showed that the length of target gene was 534bp and the nucleotide had a relatively high homology with the corresponding gene from other TGEV strains according to the nucleotide and deduced amino acid sequences. The site A gene were cloned into the vector peasy-T and the recombinant expression vectors were constructed successfully.【CONCLUSION】The construction of recombinant expression vectors filled up a gap of the study on site A of S gene in China. It also could provide a technical basis for the diagnosis of TGEV.