Oligochitosan (OC) could regulate plant defense responses in many aspects, but the basis signal transduction pathway is still unclear. In this study, we use transgenic (TG) tobacco as plant material whose OIPK gene was inhibited by antisense transformation, to identify the role oligochitosan induced protein kinase (OIPK) played in OC treated tobacco plants. Pathogen-related (PR) proteins enzymes activity assays and reverse transcriptional polymerase (RT-PCR) were conducted to compare the differences between TG and the corresponding wild type (WT) tobacco plants. Firstly, it was validated that OIPK could induce Phenylalanine ammonialyase (PAL, E.C. 220.127.116.11) and peroxidase (POD, E.C. 18.104.22.168 ) activities in respect to both activation time and activation fold after OC treatment, while OIPK had no influences on polyphenol oxidase (PPO, E.C.I.14.18.1) activity. Secondly, it was found that in TG tobacco, there was nearly just basis pal transcriptional expression after OC treatment, which showed that OIPK could determine pal gene expression in some sense. Thirdly, OIPK could enhance defense related gene transcription chi and glu activation intension and rapidity.