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Rapid, sensitive, and low-cost in vitro screening is vital for controlling Helicobacter pylori (H. pylori) infection and guiding eradication, yet remains challenging. Here we report a high sensitivity lateral flow immunoassay (LFIA) based on a multifunctional composite magnetic-fluorescent probe (MTQD-Ab) that enables accurate detection of H. pylori in stool with minimal pretreatment and supports two modes-rapid screening and precise quantification-tailored to different use scenarios. The probe features a core-shell-biorecognition architecture: a 200 nm Fe₃O₄ core for strong magnetic responsiveness, multilayer carboxylated quantum dots (QDs) for intense fluorescence, and specific antibodies on the outermost QD surface for rapid capture of H. pylori, providing dual signal amplification via magnetic enrichment and fluorescence enhancement. By functionally switching the MTQD-Ab nanolabel, the platform provides two modes: in the direct mode, sample dilution achieves a limit of detection (LOD) of 100 cells/mL within 15 min; in the enrichment mode, magnetic concentration of a 1 mL sample lowers the LOD to 10 cells/mL and eliminates potential hook effects, enabling accurate quantitation. Validation with 40 clinical stool samples demonstrated reliable accuracy and near PCR sensitivity while shortening total time from several hours to ~ 30 min and reducing cost, indicating strong potential for clinical application.