Abstract: The samples of the citrus bacterial canker disease(Xanthomonas campestris)collected from Fujian. Sichuan and Anhui in China during 2002-2003 were determined by PCR using one pair of specific primers(P1/ P2)designed based on published sequence. PCR amplification product of 493 bp target band was generated from target pathogen of X. campestris but not from non-target pathogenic bacteria of X. oryzae. Resucts showed that there was a remarkable homogeneity among the pathogens of diseased citrus from Fujian, Sichuan and Anhui, and there were specificity and sensitivity to detecting pathogen DNA of X. campestris by using PCR.