Transmissible gastroenteritis virus (TGEV) and porcine respiratory coronavirus (PRCV) share high homology and can induce almost uniform neutralizing antibody in infected pigs, which constitutes an important problem for the differentiating of the infection by which one.This study expressed respectively by tandem repeat of the C (absent in PRCV) or D antigenic site of TGEV spike protein in Escherichia coli.Antigenicity analysis showed the tandem repeat of C antigenic site could only react with anti-TGEV serum while the tandem repeat of D antigenic site could react with both anti-TGEV serum and anti-PRCV serum.The two proteins of tandem antigenic site could be used as potential diagnostic antigens for differentiating TGEV or PRCV infected pigs.