Faced with increasingly serious drug resistance and environmental pollution, there is an urgent necessity to develop green and efficient pesticides with new mechanisms of action. A novel antibacterial nano-system for plant protection based on photodynamic action was prepared by grafting hematoporphyrin (HP) onto modified chitosan through ester bonding. The self-quenching effect caused by aggregation of grafted HP could effectively inhibit its photodegradation, thus enhancing its photostability. The breakage of ester bonds induced by enzyme stimulation at the sites of bacterial infection could trigger HP release exerting an efficient photodynamic effect. The antibacterial experiments showed that the nanoparticles (NPs) have good photodynamic antibacterial activity, and the inhibition rate was as high as 96 % after 60 min of light exposure. Adhesion and safety studies have shown that the NPs are well retained on plant foliage without causing damage to the crop. Thus, NPs have great potential in sustainable plant disease management.