Nanoplastics pollution is a global issue, with the digestive tract being one of the first affected organs, requiring further research on its impact on intestinal health. This study involved orally exposing mice to polystyrene nanoplastics (PS-NPs) at doses of 0.1, 0.5, or 2.5 mg/d for 42 days. The effects on intestinal health were thoroughly assessed via microbiomics, metabolomics, transcriptomics, and molecular biology. Our study demonstrated that the administration of all three doses of PS-NPs resulted in increased colonic permeability, heightened colonic and peripheral inflammation, reduced levels of antimicrobial peptides, and shortened colonic length. These effects may be attributed to a reduction in the abundance of probiotic bacteria, such as Clostridia_UCG-014, Roseburia, and Akkermansia, alongside an increase in the abundance of the pathogenic bacterium Desulfovibrionaceae induced by PS-NPs. Furthermore, we underscored the crucial role of histidine metabolism in PS-NPs-induced colonic injury, characterized by a significant reduction of L-histidine, which is closely related to microbial ecological dysregulation. Corresponding to microbiota deterioration and metabolic dysregulation, transcriptome analysis revealed that PS-NPs may disrupt colonic immune homeostasis by activating the TLR4/MyD88/NF-κB/NLRP3 signaling pathway. In conclusion, this study provided novel insights into the mechanisms by which PS-NPs disrupt intestinal homeostasis through integrated multiomics analysis, revealing critical molecular pathway and providing a scientific basis for future risk assessment of nanoplastics exposure.