Harpins can induce systemic acquired resistance (SAR) pathway on scores of non-host plant, provide protection against a range of pathogens. In this study, we demonstrated that applied recombinant HarpinZ Pseudomonas syringae pv. tomato (rHrpZ) on tobacco with three kinds of methods: infiltrating from micro-pore into leaf; injecting into petiole, and spraying on leaf, there is great difference in assimilation of protein because of the poor osmosis of tobacco leaves, and with multi-application of rHrpZ, the stimulation effect decreased. We prepared poly d,l-lactide-co-glycolide nanoparticles containing rHrpZ (rHrpZ PLGA NPs). To study the drug effect, we analyzed the change ratio of phenylalanine ammonia lyase (PAL) activity and PR-5dB gene expression after administration of rHrpZ and rHrpZ PLGA NPs on tobacco leaves. The results show that rHrpZ could elicit a rapid and transient increase in both PAL activity and PR-5dB expression, but the effect decreased after multi-application. While sprayed rHrpZ PLGA NPs on leaves, both the change ratio of PAL activity and PR-5dB expression were comparatively smooth and durable. Our study suggested that rHrpZ NPs could help protein enter leaf epidermis and cell wall, release rHrpZ in situ continuously, and enhance the bioavailability of rHrpZ.