Accurate diagnosis of disease is crucial for high-quality healthcare services. Biosensors based on colorimetric signals made efforts to rapidly and accurately analyze clinical biosamples. Herein, a microfluidic chip for multicategory marker diagnostics is presented as a platform for the in situ synthesis of MOF-Assisted Reduced Snowflake-like copper nanoparticles (MARS-Cu). MARS-Cu can be rapidly synthesized in 40 s at room temperature and atmospheric pressure and possesses the property of "reversibility" with valence manipulation. The versatile, rapid (approximately 25 min), and multicategory determination of procalcitonin and ascorbic acid using a MARS-Cu-based sensor in a microfluidic chip has been achieved for the accurate assessment of sepsis. The diagnostic accuracy of sepsis was increased from 84.3% using the procalcitonin indicator to 100% using two clinical indicators. The strategy implements "one-chip operation" and "multi-category analysis" and effectively serves as a robust tool and timely strategy for clinical diagnostics and ensuring public health safety.