Polygalacturonase-inhibiting protein (PGIP) can inhibit the activity of pathogen PG and improve the plant resistance level.(1)A novel PGIP gene designated as CsPGIP was isolated and characterized in Cucumis sativus L.The cDNA of this gene was 1 026 bp with an open reading frame of 987 bp encoding a 328-animo acid polypeptide.The deduced amino acid sequence of the gene contained the typical domain of xxLxLxxNxLt/sGxIPxxLxxLxxL and belonged to Pgip gene family.(2)Phylogenetic analysis revealed the significant evolutionary homologous in the sequences of melon PGIP gene and PGIP genes in Cruciferae.(3)Real-time quantitative PCR analysis showed that CsPGIP transcripts were expressed in all tissues,but the transcripts were most abundantly expressed in the young leaf but much less in stem.The expression level of the mRNA could be up-regulated significantly after treated with pathogen and salicylic acid (SA) compared to the normal growth environment.The results indicated that CsPGIP might play an important role on host resistance against pathogen.