The utilization of nonmetallic inorganic nanomaterials for antimicrobial photocatalytic technology has emerged as a promising approach to combat drug‐resistant bacteria. Recently, g‐C3N4 nanosheets have attracted significant attention due to their exceptional stability, degradability, low cost, and remarkable antibacterial properties. In this study, a facile electrostatic self‐assembly approach was utilized to functionalize ZnO nanoparticles with g‐C3N4 nanosheets, resulting in the formation of g‐C3N4@ZnO nanoparticle composites. The Z‐shaped heterojunction architecture of these composites facilitates efficient separation of photogenerated electron‐hole pairs and enhances visible light catalytic performance. Moreover, the formation of the g‐C3N4@ZnO heterostructure showed a higher photocatalytic capacity and the generation of reactive oxygen species than g‐C3N4 nanosheets. The photocatalytic antibacterial mechanisms of g‐C3N4@ZnO at the transcriptomic level primarily involve disrupting bacterial membrane synthesis and inhibiting motility and energy metabolism. Therefore, the antibacterial mechanism of g‐C3N4@ZnO can be attributed to a combination of physical membrane damage, chemical damage (ROS enhancement) and inhibition of chemotaxis, biofilm formation and flagellar motility. These findings collectively provide novel high potential and insights into the practical application of photocatalysts in plant disease management.This article is protected by copyright. All rights reserved.