The aim was to study the detection technology of Pseudomonas syringae pv. in cucumber, and provide the method for quick and precise detection. According to the differences in 16S-23S Ribosomal DNA Intergenic Spacer（ITS）sequences of Pseudomonas syringae pv. and other cucumber pathogens, a couple of specific primers of PLf1/PLr2（PLf1: 5' ATA AGG GTG AGG TCG GCA GTT 3', PLr2: 5' CTC GTC TTT CAT CGC CTT TG 3'）were synthesized. Using PLf1/PLr2 primers, only a single PCR band of 473 bp from Pseudomonas syringae pv. was amplified and no PCR band from other species. The primers could identify and distinguish Pseudomonas syringae pv. from other cucumber pathogens. The PCR-based method could be used for the accurate and rapid identification of Pseudomonas syringae pv. Furthermore, the pathogenic bacteria were detected by this diagnostic technique in 72h before syptome was observational.